Either prices are in their control and one company can gain market share by lowering them. Or they're not. I don't think you can have it both ways.

It can be a one way ratchet, which is my argument here. Regulations, medicare rates, and pricing power from drug companies set a floor for prices. Insurance companies already run pretty lean and have so-so margins. The 80-20 rule incentivizes a slow ratchet up on prices and the other factors prevent competition on price. The system is designed to have slow predictable price increases.