Are salaries the only source of income that they derive from the medical industry? My doctor is a part owner of his provider network which also is the insurer.
The big DI manufacturers have consulting arms that will help physicians with financing to buy CTs, MRI, PET, that will help them obtain Certificates of Need.
And having a hard time finding it now, but physicians who own a share in a DI lab tend to refer their patients for imaging far more generously than those who don't...