This is a fairly old source, but it demonstrates the concept.

http://www.er-doctor.com/doctor_income.html

In case people don't bother reading it in depth, here is one of it's updated links:

https://www.linkedin.com/pulse/70000-per-year-start-now-kevi...

I ran the numbers recently and the numbers were even more grim, but I'd need to track down all my sources again.

I just think the main point is that income is not the number to focus on. Wealth is the end result of the equation, and income is only one part of that.