Air medical transport is only necessary in an emergency, at which point the customer needs it suddenly and has no opportunity to compare prices or refuse service.

This is exactly the market failure that causes municipal fire departments to exist, and should be solved in the same way, potentially by just having the fire department own and operate the helicopter(s).

It's bananas that emergency medical services like air transport can be "in network" and "out of network." As if the patient in need of services has the capacity or ability to control which helicopter comes to pick them up from their near-death experience.