You've made that assertion repeatedly w/o supporting documentation of any kind.
Right now, it's just an example of Truthiness, of you believing it to be true because you want to. It's an argument based on thin air.
When an insurance co gets a bill they see as unreasonable, they negotiate. If the provider won't settle, the insurance co pays whatever they believe to be reasonable & the provider has to sue if they want more. They seldom do.
Overvolt's assertion remains bogus. Hospitals are required, by law, to treat & stabilize emergency room patients. That's covered under the ACA. Once that's done the patient is transferred to a suitable facility for appropriate care dependent on a variety of factors. It's not like the hospital in Gillette, Wyoming is going to overcharge for a heart transplant- they don't have the staff or the facilities in the first place.
I'm hesitant to step into the middle of this... but can I say that you're both not really right?
Overvolt isn't right that insurers have no ability to negotiate, in fact they have quite a bit of ability to negotiate
before the fact. We hear complaints all the time from medical providers who want to be in a network but who refuse to accept the insurer's reimbursement rates. They want us to force the insurer to sign a contract with them at their named price. We're not an "any willing provider" state, so we don't do that. But, if the insurers had no ability to negotiate then it wouldn't even be an issue (from the providers' perspective).
At the same time, insurers don't have the ability to negotiate that you think they do. From an insurer's perspective the provider is either in network or out of network. If they're in network the insurer pays the pre-negotiated rate. If they're out of network the insurer pays the usual and customary rate (which, coincidentally, is close to or the same at the in-network pre-negotiated rate...). If a provider is out of network the insurer won't negotiate with them and their only recourse will be to balance bill the patient (in states that permit balance billing).
With that said, neither are hospitals bargain bastions. Hospitals can and do gouge customers at every opportunity. Anecdotally:
One hospital near me is the dedicated regional trauma center. If you go to that ER by ambulance (ground or air) they charge you $2,000 automatically for a "Green Trauma Team." The charge is incurred regardless of whether you are brought in as trauma or not. You cannot negotiate out of it and the courts will not intervene, it is legalized extortion.
The hospital closest to me was just recently named the "Most Expensive Hospital in America." If I go there for a non-trauma ER visit or some procedure that requires an in-patient stay I know I'm going to get ass-reamed.
We have lots of rural communities that are underserved medically. In one of them the only doctors that perform colonoscopies do so at the local hospital. It costs over $3,000. If you drive a couple of hours to a major city you can have the same procedure done for $800.
Moral of the story: nothing is ever black or white, it's all shades of gray (and a hell of a lot more than 50 of them).