In the case of medicine, this may be illustrated by considering that there are two significant income threshholds for medical professionals:
What happens, really, is that the country has considerable capital in the form of people with doctor-level medical training. If physician salaries are constrained to be below the point where few new people choose to enter the field, that capital base will be eroded. It won't show up on any balance sheet, but once it's gone there will be no way to repair the medical establishment without spending money somehow to rebuild that capital base. Of course, those who seek to do that will be accused of causing the problem in the first place.
Isn't that already happening? I seem to remember Dr. Dean Edell mentioning that medical school applications are down, not to the point that we're about to suffer a doctor shortage, but forcing the schools to be less selective about admissions, so the overall quality of students (and future MDs) is lower.