system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why have the salaries of athletes, actors, TV personalities, musicians way outpace salaries of traditional occupations over the past 100 years?

In the peak of his career, Babe Ruth (highest paid at the time) made $80,000 a year in the 1930s which is equivalent to a little over $1 million in today's dollars. Today the highest paid baseball players make $30 million+ a year.

In 1937, the highest paid actor was Gary Cooper and he made $370,000 which is equivalent to about $6 million today. In 2016, Dwayne Johnson was the highest paid actor making $65 million in one year.

This is while the average salary (adjusted for inflation)for traditional jobs hasn't risen much in the same time frame.
gpt
Increasingly, salaries are tied to how replaceable we are rather than anything about how hard our job is or how much work is involved. Cleaners work very hard and long hours, but you can get someone else in to take over a job immediately with little training if someone quits, so they are paid crap money. Doctors/nurses/teachers are always in high supply because they are jobs that people want to do regardless of the pay, so they don't get paid much either. 

Celebrities that bring in lots of money for companies because of who they are as individuals are quite hard to replace. If you don't pay Dwayne Johnson enough to do the job you can't get another Dwayne Johnson. With movies, particularly, up until around the 60s (not exactly sure) there used to be a studio system where an actor/musician/director/writer etc. would sign a contract with the movie studio and they couldn't do a film for another studio until their contract was up or the studio allowed it - it's a bit like comic book movie franchises at the moment. Because actors were contractually tied to studios they couldn't demand ridiculous salaries or threaten not to make the movie, and when there are only a handful of studios the bidding wars can't really get that high when contract renewals come around.