IIUC, the dynamics are the same as with most other businesses:
- Seller sets prices to maximize profits. If possible, on a per-market-segment / per-customer basis.
- There are no laws (AFAIK) enforcing price caps, aside from what Medicare will pay.
- Seller has a temporary monopoly on some drugs via the government -controlled patent system.
- Seller is a for-profit corporation.
So what do lawmakers expect???
They made the rules, and are uniquely empowered to change them if they don't like the resulting market dynamics.