Except it is not a free market. Providers cannot ban together and refuse to accept insurance, but insurance companies can peg their payment to medicare in lockstep and that is not considered price fixing.
It's only legal because of lobbying. We need to get rid of insurance companies full stop. There will always be a private cash market and prob some add-on insurance-like options (akin to Rx programs that are negotiated plans but are not classified as insurance). Providers will always be outgunned against trad insurance companies, so we need to be smarter in how we interact with them and we need to find alternative opportunities so we are not dependant on them.
The dirty secret of insurance companies are they *do* pay some providers significantly more than others, but you need to do your homework first. It also helps to work in niche speciality areas and expand your offerings.
When I took insurance, I negotiated to take 5-6 plans, all had to beat Medicare rates. After a year or so I renegotiated. I dropped all but 3, and negotiated higher rates. I since relocated and built up a new practice that doesn't rely on insurance for cases or income.
There are sometimes options to do one-off contracts. For instance, I did some one-off contracts for my cash rate bc they didn't have in-network (neuro) providers in my area and they were desperate. I did this with a few smaller plans that were covering satellite offices.
Often companies will buy "access" to an existing network to cover workers in satellite offices geographically far away w/o coverage from the primary network. If you can identify these businesses, you can often negotiate your own deal bc a lot of networks offer junk coverage and/or lack local resources.
HR ppl and in-house legal have consistently been great contacts bc they often can push right past cost if you can fix their problem. EAP, fitness for duty, return to work, etc. Doctorally-trained clinicians have a lot to offer, you just need to know how to return skills and package it to prospective parties.