Doctors' profession have artificial barriers to entry and keep the supply limited, in many other countries, but even with those, they won't dream to earn anywhere near 500k.
It's 100% true where I'm from in Europe. The government opens up only a fixed number of residencies positions every year regardless of how many more students graduate (cartel behavior from the national Doctors' association).
My cousin graduated med-school last year and is still unemployed because no hospital had a place for her. Private practices don't fix that issue since they're not designed to be part of the medical teaching cycle. So a lot of young doctors have to emigrate to other EU countries where they can find spots to practice.
This is orthogonal to your GP point which was about salary. There are a lot of issues with the teaching pipeline AFAIUI so it is difficult to comment on n=1 examples.
The other developed countries doing this don't pay dermatologists 500k though.