Shredhead, you are correct that doctors doing stem cell therapy are mostly cosmetic surgeons. That is because they are the only ones trained in liposuction which is the hardest part of the process.
There is also a procedure where they extract marrow from your hip and distill the stem cells from that. However, from what I have read there are more stem cells in stromal vascular cells (SVC) than marrow. A nice side effect of the procedure is you get rid of your 'love handles'.
As for cost, yes it is expensive but depending on your deductible, it may not be that much more expensive. Insurance covered my Synvisc inspections but copay was still almost $2000 because we had not met our deductible. That's another reason I went for the stem cell therapy, I was looking at another $2K for another round of Synvisc that would only last six months.
Right now my right knee is pain free and up until my latest accident so was my left knee.