It's fair if you choose to become a doctor knowing that you will only ever get same wages as everyone else. You would do it because you want to be a doctor rather than for the money.
No it's not. That's just your idea on fairness.
Opinion on fairness is not only subjective but subject to change as well. It's easy to think it's fair before you start studying to be a doctor to only come to a realisation of how unfair it is once you go through it.