Saving a life creates some aggregate economic value (the person will not die and instead will continue contributing to the economy for X more years). Drugs are expensive because in the first world, that amount is a lot and the entity creating a cure can reasonably expect to capture a substantial portion of it, either because the person will pay it or because governments will.
Neither is intrinsically a problem. $84,000 to cure HepC is a bargain, because people die from that quite young and on the other side of the equation is potentially millions of dollars of saved economic productivity. That’s not an argument for not charging $84,000 for HepC drugs. It may well be an argument for having the government foot the bill.