Keep in mind that the potential for huge profits was what motivated private investors to fund development for a cure. Without that, Hep C would still be a death sentence, regardless of how much money you had.
https://www.sec.gov/Archives/edgar/data/882095/0001193125113...
It sort of looks like they have figured out how to have excellent pricing power when they are willing to bid $11 billion for the company. Part of that is probably that looking just at this drug is a facile analysis of the value of Pharmasset (which did more than develop 1 drug, they built expertise in creating antivirals). Of course, the expertise story implies that they don't need to recover the purchase on just this drug.
I guess some of it is the complexity in the medical payments system.