Except the cost of many drugs continues to go up, even as they're commercially available and R&D has been recouped

A successful drug doesn't have to recoup its own R&D costs, it also has to recoup the costs of all the drugs that failed to make it to approval. It's not any different than VC investing. Just because one company in a portfolio returned 10x ROI, doesn't mean you can be like "alright guys, you made back all your money, now turn yourself into a non-profit".