It's the administrative apparatus of hospitals. Not only doctors, but staff, admins, real estate, etc. Notice how swanky some "clinics" are? Also doctors' pay

It's the administrative apparatus of hospitals. Not only doctors, but staff, admins, real estate, etc. Notice how swanky some "clinics" are? Also doctors' pay does grow at super-inflationary rates according to data. That's at least part of the story.