I'd chalk this up to the kind of "creative accounting" they do in the movie industry. But that's just a guess, I don't have any knowledge on the matter.
A small percentage of hyper inflated prices over a large consumer base still equates to MASSIVE profits. It is a fundamental ethical flaw that we even allow for-profit medicine that is compounded by obvious cartel organization structures and corruption.
Some of that is "clever" accounting, the rest is that healthcare insurances don't have bargaining power with the providers. In Germany the state insurance companies have collective bargaining power so that for example an ambulance ride costs 500€ instead of 15000.