doing an X-prize style competition will probably cause a lot of "wastage" in resources spent by other contestents that _almost_ get the cure, but didn't make it. It will mean that only those who _know_ they have the cure (or it's within reach) would invest in it, and hence, won't get cures for diseases for which we don't know much about. I reckon better way is to have publically funded labs that do the lions share of research, budget split by how common the disease is.