In 2030, would we as a society rather have a generic, cheap, openly available HepC cure or not? That is the question you need to ask, and I don't think anyone would say no to that. The $84K drug will fall off patent by then, which means the system we currently have, flawed as it is, will produce that outcome.
It doesn't cost $84,000 to manufacture that drug compound. That $300 one even has the expensive drug formulated in it! The $84,000 covers the cost of developing the drug, along with the 56/57 other drugs that generally fail for every one that hits the market, along with a profit incentive to run a pharmacuetical company in the first place. And yes, it's grossly unfair for the patients currently requiring expensive treatment, though solving that through insurance is almost certainly a better idea than regulating prices. If you start regulating drug prices, as have many other countries outside of the US, you disincentivize development.
If there is a better way to create cures, that would be wonderful, and I think we would all welcome suggestions. However, there is a reason the US invents the majority of the world's pharmaceuticals. Nothing to date (everything from regulating prices aggressively to prolifigate government spending projects) has worked as well as what we have now for long term results.