This is partially true, but this example also shows the brilliance and foresight of the American Board of Dermatology (or whatever it's called) to severely limit the amount of dermatologists produced every year.
By consciously limiting the number of [derm] residency spots to around 225/yr for many decades, it has allowed derm. to be the field sought by the "brightest" medical students, knowing that when they graduate, they will be able to command insane salaries and walk into a practice with a 3-4 month waiting list.
Believe me, the US could support 2X the number of dermatologists right now, but their mean salary would decrease appropriately.
But I digress.