Actually, the doctor analogy is a fair comparison in that these Medical practices work for a medical group ( in my area Axeminster, Providence, Torrance IPA, etc.). The medical group is like the AMC, only paying out so much per patient visit. In other words, the doctor has no control of how much to charge for his services.... they only get what the Medical Group gives. Why do you think when you go to the doctor you're seen by a nurse practitioner?
Many doctors have bailed on practice and gone into being the university professor..... more money in it.