Basically, your compensation is based on the face-value of the results of your work, as well as the difficulty necessary in order to be capable of doing such work. So for other positions that require more work-per-hour, they get less usually because a greater population is capable of that same work. (and so, someone somewhere can be found to do it cheaper)
I think that seems to be missed a lot in discussions of this nature, the value of training and the scale of populations with given skills and how more training generally means less people and therefore less who are desperate and will take a lower than standard wage. (while with unskilled positions, it's automatically a race to the minimum)
I don't have an objectively provable rule, but I do have one that makes a pretty good starting point: if you create something valuable, you should be able to capture most (or even all) of that value.
of course, no one just creates things from scratch. they use tools designed by other people, they use resources extracted from the earth, their productivity might be multiplied if directed by a good team leader, etc. if you take the final product and subtract all the tools, resources, and infrastructure used, you have your personal contribution. I think we should strive for a system where the worker keeps as much of their contribution as possible. some people's contribution will be much larger than others', depending on their skills and the type of work they do, but I don't think this is inherently unfair if you have first accounted for all the external things they have benefited from.