This part of the puzzle is still missing. IIRC the providers are required to use patient's insurance (and the associated prices), when patient does have an insurance. So, for example, if cash price is lower, than the effective negotiated price (factoring in the deductible and copay), one would still be required to pay the insurance-based price. Granted, in most cases patient would have no idea about what are those prices are until getting the bill. Hopefully, this part will get more transparent.
This is especially noticeable with the high-deductible plans available under ACA.
It's getting harder and harder to clearly see the interests of providers and those of insurers separately from each other. Especially with the recent consolidation in the healthcare sector.