You can also look at public incomes of physicians in for example, transparent california. Single phsyician practices with over 1mil in income is pretty common.
Reimbursement is set by the fed (medicare rates) and ins cos base their rates off of that.
https://www.bls.gov/ooh/healthcare/physicians-and-surgeons.h...
It would of course take a hell of a lot of variance for a significant percentage of doctors to be pulling in a million plus. With 713,000 working doctors, there will be a fair number pulling in lots more than average.
https://transparentcalifornia.com/salaries/search/?q=PROF-HC...
I've linked the mean salaries for the US as a whole.