Insurance companies generally have regulated profit margins. Healthcare providers don’t. However, note that this is all percentages — if the total cost of healthcare goes up, providers and insurance companies both win in absolute dollar terms.
Great point on bigger pie increasing both shares. I didn't mean to imply it's zero sum.
Oh the irony of MLRs encouraging insurers to provide terrible service (opex recovery boosts profits) and let providers push fees ever upward (bigger pie, bigger premiums, bigger net profit on constrained margin).