This is one of many reasons why selling on ebay can be a hassle. You can be as honest as possible and still disappoint people.
I recently auctioned off a couple of plants and received this response from one of the winners.

Dear fmen2007,

Dear Seller, Got the plant. Box was in good shape.
I know you have several plants of Kathleen Black.
Despite that I paid the top price for it, $112.50, despite that i wrote to request a choice plant you have for the top price, I am very disappointed that you gave me the least desirable plant.
I have bought all the name species of figs on eBay.
Your plant is the least good looking, though the most expensive I paid.

How does one respond to something like that without worrying about negative feedback?

Hard to say without seeing the original description.  I would ask what is specifically undesirable about the tree?  Does the auction description match the tree?, if so, it is a good sale and you can mediate through eBay.  Having sold over 1000 items on eBay over the last 13 yrs, I can tell you that there are risks and you have found one of them.

If the tree matches the description, then it sounds like buyer's remorse, or as I call it, spouse found out how much was spent on a tree.

If there is any doubt, offer a discount or refund to preserve your rating.

You cannot control what people write. I've noticed recently that eBay bidders get into this bidding frenzy and get caught up in the "I must have it at any price idea".
I would never retract a bid on eBay unless it is a typing error. If someone keeps bidding up the price, it is his responsibility to know that he is putting himself ahead of someone else who also might be interested in that item.
They say that timing is everything. If I find out that I paid $112.50 for something that someone else ends up getting at a fraction of the price at a later auction, then it is my fault and only my fault for allowing myself to pay that much. So disappointment is a natural reaction at that point. Looking for any excuse to get out of an auction by abusing the seller is a low blow.
In any case, if it was me I would negotiate with the buyer and see if I could reach a reasonable solution. In the end a 100% feedback might be more valuable than his $112.50.

Bad Frank:)

 Ebay is a hassle. My wife sells stuff on Ebay ( not figs or plants) and although she has great feedback some of the BS she has to go through is crazy. She has even had people complain let them return a item that was not even the same item she sent!!  Ebay seems to always side with a buyer if a case is opened.

I think I would send them Pictures of all my 1 gal plants and let them pick, pay shipping back to you for the original plant, then ship them the one they choose. I REALLY doubt you sent them the least desirable plant, and how would they know... It's buyer remorse as stated above.

I would as well do what you did on your present listing a picture of the actual tree. I know that's a hassle but it really resolves any questions. Including photos of a mature tree, fruit is excellent as well, but at least one photo of the actual tree being sent, same with cuttings or anything else. Again a hassle, but if not there are always those that will complain,

Thanks for the feedback, all.
This is the original auction. I had two pictures of the plant.
http://www.ebay.com/itm/261321294144?ssPageName=STRK:MESOX:IT&_trksid=p3984.m1559.l2649

This is my current listing to a very similar looking KB. 
http://www.ebay.com/itm/261331393756?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649

You be the judge.

This is what I was planning to respond. 

Dear buyer,
Sorry for your disappointment. I am curious as to how you know I have many more KB's and that I sent you the poorest one. It is in fact true that I have a few others, and I currently have another on ebay, but is very similar to yours. I have smaller and weaker plants and I have 1 or 2 larger plants that have not yet fully established good root growth from fall air layering. I have a huge one in a 5 gallon pot promised to a local buyer.
It is against ebay policy to show pictures of the item that is for auction and then send a different item. I mentioned this in my response to your first email.

 I am glad it arrived in good shape. The good news is that under proper conditions, this plant can grow to 3-5 feet by next year and possibly produce its first fruit. I was able to grow the mother tree which  is now over 6 feet tall with multiple branches that produced dozens of figs from a small cutting in just 2 years time.

Let me know if I can send you cuttings of another variety to make up for your disappointment.

Frank

Frank
You are clean on this.  No doubt!  Good response.

If the item shipped matched exactly the description and/or picture
in the listing; you should have nothing to worry about.
[E: Also check your return policy on the original listing.]

The comment from the buyer seems like nitpicking.  KB is a strong-growing and healthy cultivar.  As you mention in your response, as long as the plant you sent is healthy, and buyer knows what they are doing, it will put on lots of growth next year and all of this will be long forgotten.

Having sold thousands of items on ebay and dealing with customers such as this from time to time, it is best to negotiate even if you are 100% right. Leave out the first paragraph of your reply.

Frank,

Looks like the buyer saw your new listing and decided to take a crack at it in an effort to get an exchange.

What's done is done.

If you get a negative feedback because of this then so be it. Like the other said above: buyers remorse.
And if there is a negative feedback then throw a response to it saying item shipped as described.

In the future you should add more pictures of the actual plant from different angles and tell them this is the actual plant that will be sent. You cannot over disclose when selling on ebay. The more the better.

Good luck my good friend. I know you are a genuine person and an asset to this fig community.

Frank, that's a shame.
The following is a message for the buyer, just
in case they read this post:

What's the matter with you?
Frank has a good reputation, he sent you
a KB, a variety that lots of people are obviously
willing to pay top dollar to acquire, and now that
you're looking at the plant, and it doesn't have 40
ripe figs hanging from it, you're giving him
a hard time?!
Look, the plant grows quickly, take good care of
it, and learn from your experience. Nobody forced
you to bid on it. Call it an early Christmas present
to yourself. By next year, you'll be saying it was the
best $100 you ever spent.
I don't know Frank personally, but I know he's a good
man. But he's not your father. This was your decision.
You are going to give yourself a bad reputation.
Be an adult.

Hi Frank,
Sorry to hear of the hassle.  As for response to the buyer, I agree with most of the comments above.  Still, Rafed's advice was good for ways to reduce the incidence of similar things in the future (more pics from more angles, to which I'd add you could consider fewer pics of anything that's not the actual tree they'll get, and clearly indicate which pics are not the actual item), but of course no matter how much of those sorts of things you do, you will still get some amount of this sort of response.  Because it's not really about how well you did with your auction, nor how honest you are (which I know to be highest caliber).  It's about that buyer's response, which you cannot control, and can only minimally influence.  I also agree with the suggestion about toning down your first paragraph... you can probably make the same point a little more sparsely and neutrally  (e.g. "Sorry to hear you're disappointed.  I think the one I sent you was the best tree.  The other one that I'm selling on ebay is very similar, but not better.")   But of course it's up to you how you respond, Frank.

I boil it down to this:  You can't please everybody.  There is after all another person involved, and you can only choose your own actions, not the other person's.  I think you're spot on, so don't take their response personally.  Your offer to find another way to please them is generous.

Mike   central NY state, zone 5a

I think the buyer is saying that of all the ebay figs trees he has bought, yours was the most expensive and the least impressive/desirable.  I don't think he means you sent him your worst. 

Encourage him that he paid a premium because of the variety, that the young tree is healthy, and that wiht time (rapidly) he will find your tree compares well in vigor to the others he has bought. 

Play nice, but you can't please them all.

Frank
I have run over 1000 auctions on eBay and one thing is for certain. You can not please everyone. There are some people who are  un pleaseable. Usually throwing some money at it smooths it out. Not fair mind you, but we all just want to be done with it.
Its part of the business.

To me the photo of the plant was taken from the top and  he may of thought it was bigger, more photos may have avoided this....just my 2 cents........ I don't know how to remedy this,.........................  I may state that, "I am sorry that you are disappointed with the tree. What do you feel can remedy this purchase. I do want to keep you as a future customer."     

So Frank you sold a fig tree and the customer had buyer's remorse or he imagined it was bigger.     Good Luck Frank !!!!

i think a couple of good pictures of the plant to be shipped would be the safe thing for you. then if the buyer is not happy it would be on them. sound like someone that hasn't  done cutting before. keep it simple for the new person. good luck

Hi frank,
as an experience eBay Buyer, I will tell you that the person bid with out looking at the picture, and after the bid ended he realized he did not see your pictures in full , so he asked  you to switch the plant for him to justify the amount of money he paid, you did not comply...he got nasty. I wear my heart on my sleeve, my advice might not be the logical choice , but the buyer is an adult that did not do his/her homework, and wanted a  get a free out of jail card...on principle he has no business twisting your arm , case close. and be adviced that this person is a member of this forum and probably read your thread about KB that you have while ago, and he/she reading this thread...
Mark

Ridiculous!

Suck it up, you bought the plant, next year coming out of dormancy it will explode with growth and by the end of the season it will be the same size as any other KB of similar size and or age. The hours of time spent rooting and watering a cutting are worth what you paid for it. If you pay more than $100 for a plant, it means you have more money than time and you paid Frank for his time...PERIOD. Otherwise you would have bought cuttings and did it yourself. Buyer, your train of thought needs to be "Oh..I thought it would be bigger. Oh-well I have an established KB ready to rock for next year."

I would say if you don't like the one you got in the bid, then bid on the other one that is up for bid now. LOL

Frank,

In looking at the bid history there is no way the buyer had any doubt about how much he/she was spending. This is a definite situation of buyer's remorse. I just did the same thing myself bidding on MDDS, I got outbid and then was offered a second chance and took it, then what do you think but another was put up at the original price. But I have sold on Ebay and I know how important it is to keep a good rating. (It's absolutely crucial!)

It's just like being a waitperson or working fast food, everyone should be one so they understand what it's like. So too should a buyer on Ebay be a seller first! You have been given good advice about showing actual pictures of the items being bid upon, which you did but they were not the first pictures. The buyer most likely didn't even scroll down to look at the second row of pictures. I hope the Ebay resolution folks do the right thing by you. They probably see this thing every day. I had a person cancel a purchase and leave bad feedback but they ruled in my favor and their feedback was removed.

If only everyone would live by Golden Rule: "Treat others in the same way that you would want them to treat you." ~Jesus Christ

Hey guys and gals, you rock! Thanks for the affirmations and suggestions.  The mini drama is over.
I responded to the buyer as above and he wrote back with the opening line, "Thank you for your gracious reply."
I will send him some KB cuttings when dormant. We may even do some trades in the future. All's well that ends well.

In the future I will make it abundantly clearer that what you see is what you are getting vis a vis the pictures. I always include an 18' ruler next to the plant to indicate the size.

Rafed, my friend, glad to see you posting again! You have been missed. I hope that you and your family are starting to recover from recent events.

Frank,

That's good news. BTW, I just marked you as a favorite seller:)

Frank,

Good for you, glad that it worked out the best for both of you.  Even though I don't think you owed this person anything it was very good customer service offering cuttings to make this person happy.  Now having said that, I would say nobody twisted this person's arm to pay that price for the tree.  Also like other have said, it is a pain but post plenty of photos of the offered item next time to prevent people from making "whining" claims. 

And last, I know that this may not make sense, but who cares if you don't have a perfect eBay rating.  People on this website, and I know not all fig cutting/tree eBay buyers are on this site, know you.  I'd still buy from you, cause I know the type of person you really are, not what some silly eBay rating "says" you are.