If you have a hospital with a certain list price for a particular procedure, why is it legal for them to charge one insurance company 5% of that price and charge another insurance company or someone without insurance full price? It seems like exactly the kind of scenario that price discrimination laws are meant to prevent.
Similarly for the insurance plans themselves, why can you sell basically the same plan to employees of a large company for much cheaper than you sell it to employees of a small company? (This one might need to be a new law specific to insurance companies, because clearly there are many other products that give group discounts when selling to large companies, but I think health insurance should be treated differently).
I'm sure I'm missing what some of the downsides might be, but it seems like making these kinds of backroom network-based deals illegal in health insurance would go a long way in making prices more understandable/predictable, and that might allow for more fair competition on price to emerge.