i think basic math is to say.
these days most pro athletes go to prep high schools for sports, right? so they pretty much start training to become a professional athlete when they are, say, 14 or so. doctors, lawyers, teachers, etc. don't start training to be those things until college, or even grad school in many cases. lets put it at 19 to be kind and assume that all doctor's, lawyers, teachers know right away they want to be those things and choose their major in college accordingly. that's still 5 less years than the pro athletes spend training for what they do. and, in reality, lawyers, teachers, doctors don't start training for their profession right when they enter college, especially lawyers and teachers. doctors do to an extent just because they have to do the pre-med tract in college in order to get into med school.
on the other hand you can easily say that all those professions require you to work very hard to succeed, because they do, and that it deserves to be compensated for. i mean, lawyers and doctors do make a lot of money, too.