I am in my third season of rooting cuttings, so I can only give you my own subignorant point of view.
Season 1: 100% mortality. I used peat moss instead of long fiber sphagnum moss and kept it too wet.
Season 2: didn't keep records, but I'd guess 70% cuttings from same tree rooted. About half of those made it past cups. All that made it to soil in pots are alive today. Rooted in perlite, cupped perlite/vermiculite, potted happy frog soil.
Season 3: separated cuttings into batches and experimented with a few different techniques. First three trials had around 90% mortality due to mold. Last trial used rigorous preparation in rooting cuttings in damp, chopped sphagnum. So far about 80% are already in cups. Those that are not rooted yet just started showing signs of activity today so might get close to 100% of this batch rooted!
What I'm getting at is that very high success rates are obtainable, but it depends on the cuttings, the current conditions, time of year, and what YOU put into it. Like Harvey pointed out, a given amount of effort will produce 80% success. You can certainly improve that by putting in more time and effort (and maybe money), but 80% or even lower may be acceptable since it might be easier to get more cuttings rather than get an extra 10% success rate.
By the way, that last batch with hopeful 100% success was all cuttings from Jon. ;-)