You can look up Dr. Elizabeth Potter on Youtube who publicly details what its like dealing with insurance, and all the ways insurance screws her and her patients. United Health actively threatened and retaliated against her business when she started getting publicity.
The total industry wide profit numbers aren't relevant at all if you're running a small clinic going up against an insurance provider. Heck even if a single clinic made more money than an insurance provider, it would barely matter - the insurance providers have the power to stop covering your practice and kill it, a clinic does not have any such power over insurance providers.
And yet this has absolutely nothing to do with the claim that "Insurance companies hold tremendous leverage over care providers, up to and including the power to effectively put them out of business on a whim.", you're not even engaging with the argument at all.
It doesn't? All the money is going to them, and they're massively larger than the insurers, but it's the insurers with all the leverage? Why isn't more of the money going to the insurers then?
Do you make this argument in any other scenario? I'm sure all merchants who accept credit cards combined make WAY more than Visa/MC, but I think most would agree Visa has much more leverage over a corner shop that accepts Visa than the other way around.
There are 5 or 6 big insurance companies, maybe 2000 if we count all of the small ones and 400K medical practices. So even by this very simple money=leverage argument, each individual practice has far less money than the insurance company they are dealing with. So if more money = more leverage then these same numbers prove the opposite claim.
So its probably fair to say that the picture isn't as simple as money=leverage.
If a medical practice and an insurance company get into a dispute and one of them decides to not work together, the practice loses say 1/5th-1/10th of its customers, the insurance company loses 1/100000th of its revenue. I call that leverage.
The total industry wide profit numbers aren't relevant at all if you're running a small clinic going up against an insurance provider. Heck even if a single clinic made more money than an insurance provider, it would barely matter - the insurance providers have the power to stop covering your practice and kill it, a clinic does not have any such power over insurance providers.