I'm going to start work soon on setting up a small hobbyist nursery on our property and would eventually like to put up a greenhouse.  That said, the only option I've come across for ordering some items seems to be online: pots, heavy ground cover fabric, promix products, large bags of fertilizer/soil amendments, irrigation/fertigation products.  Shipping on these, especially for the heavier/bulkier items, is almost cost-prohibitive.

Fertrell, Lancaster Ag products, Frey Bros are all less than an hour away from you.

Griffins is in Morgantown too.

You need to locate the areas of agriculture near you =, and see who their suppliers are. Check out the local University Cooperative Agricultural Extension office, local agricultural organizations, Farm Bureaus, etc. Maybe the local Iris society (or some other cult group) buys pots in bulk, or knows a source.

Sometimes craigslist can be helpful. I have found some real deals on things such as nursery pot that way. OK they might be used, but still very serviceable, and then you are being environmentally friendly, green, recycling, and all the other buzz words. I bought brand new 15g pots from a fellow that bought them by the truckload, and paid half what they would have4 cost me when I  bought only 100. Found them on craigslist.

Generally the commercial suppliers don't want the hassle of dealing with retail customers, so they don't make themselves known through the usual "retail advertising" conduits.

For non-bulky, non-heavy items, buying online is often the most cost effective.

There is not simple answer - you just have to address each item one at a time.

Griffin greenhouse awesome dealt with them many times
Lancaster Ag. excellent source headed there tomorrow...

Tim ,
Most greenhouse growers , CSA's ,  farms , garden centers etc. near you are probably ordering from Griffin Greenhouse Supply.
 They have a weekly delivery route and require a minimum order.
 I've always found a friendly local grower who will let me order through them because it helps them make the minimum order requirement.
Look at their catalog online get all of the catalog numbers for the things you need so it makes it easy for the grower you are working with to add your order. The garden center up here who I order through doesn't add any additional charge he is just happy to help out another smaller grower.
For row cover and irrigation supplies etc...Rain-Flo Irrigation Supplies is a great family run company to work with in Lancaster County.

Thanks everyone for the input!  I had no idea that there were so many good places close by.

Tim here is the closest griffins location to you about a 45 min. ride for you. I have found that placing an order as a cash customer is no problem they will order over the phone and then you pay for it when you pick it up in a few days. cant beat the prices on the perlite. I have not been to this one but the one by me in south jersey is awesome.