IMO, it still does not change the fact that the doctors could give lower rates for people who can or have to pay out-of-pocket. There is less administrative cost for accepting cash. They make enough money off of insurance companies to still live comfortably.
They still live in nice houses and drive nice cars. I have yet to see a doctor driving an old junker or living in a low-income area.
I for one wouldn't mind paying $50 or so for an office visit as long as it helps to keep the cost of medical insurance down.
I agree with you that cash customers should have a lower rate on medical services. It would certainly lower their paperwork.