I'm no expert either, but I think the problem is that suitable donors are extremely rare -- and most of them would prefer not to give up their bone marrow to some random stranger, thanks very much.
update: Oh, and a bone marrow transplant is a horrible procedure which kills 30% of recipients.
AIDS perhaps, but anyone that could afford to pay for a treatment like this is unlikely to have progressed past HIV, as they could surely afford the best current treatments.
Disclaimer: I don't know what I'm talking about.