The more time I spend in the medical industry the better I like single-payer.
The prices are public, mandated by the state or feds, and argued over as policy. Your lobbyists, my lobbyists, your experts, my experts, your doctors, my doctors, your executives, my executives, they're all going to get together in a public space and hammer this shit out. This ICD-10 code pays this much. That one pays that much. Publish it all as a schedule on the interwebs so everyone can see it (my state already does).
Now any insurance company under the sun can bid on providing services in that state. Their profit is the difference between what it costs them to pay out those codes and what what they pull in as premiums (which are paid, in full or in part, by the state - there's another whole committee there). You can no longer make your profits by screwing patients - they aren't paying you directly. You can no longer make your profits by screwing healthcare providers - their pricing schedule is publicly available and if they gave a shot of Rhogam, you pay what the state says you pay for a shot of Rhogam.
The only way you can make money is by keeping people healthy.
Preventive care starts looking really cheap then. So does group therapy. Nutrition? Fuck yeah let's pay our nutritionist her rate and have her be at the community center twice a week. And now you have a major multinational company whose profits depend on inner-city Detroit being healthy because those guys are eligible for healthcare, and they signed a contract to provide it.
For some reason, public health is considered a private problem. But trust me: you make Aetna's bottom line depend on welfare mothers eating healthy and welfare mothers will be eating healthy.