> Insurance is the only industry where they agree to pay for something (in this case, "medical care"), but then after service has been rendered can decide to pay less, or not pay at all, or stop paying that provider altogether

This is precisely why I think we will never be able to effectively treat healthcare as a "free market" with tools like HSAs, posted price sheet, etc. The end user can never know the true cost of their procedure until it's long over (sometimes years later) and often don't get to choose at all.