Athlete wages are absolutely through the roof. It seems every other week there is a new "highest paid athlete of all-time". Recently, Matthew Stafford became the highest paid football player of all-time, and that should say something.
On top of the salary they make from playing their sport, they also receive endorsement deals or create their own branding (*cough* LaVar Ball *cough*), which only further increases their net worth. Currently, Forbes lists Cristiano Ronaldo as the world's highest paid athletes of 2017, raking in a whopping $93 million ($58 million in salary, $35 million in endorsements). On the all-time list, Forbes ranks Michael Jordan as the most prosperous athlete of all-time, racking up $1.7 billion through a combination of his salary, his deal with Nike, and other various endorsements (As of 2016).
Jordan may be the highest paid athlete in modern terms and dollars, but speaking in terms of all time there was an athlete that made much, much more.
Gaius Appuleius Diocles (who lived between 104AD and 146AD) technically made the most in riches during his time as a Roman Charioteer. The man that would come to be known as Lamecus won an astounding 35,863,120 sesterces during his 4,257 races, of which he won at least 1,462 according to David Stone Potter of the University of Michigan. Sesterces' were small coins made of either silver or brass depending on the exact time period they were used (which was brass during the period Lamecus was alive).
Obviously it is impossible to do an exact conversion of what that amount of a dead currency would translate to in modern dollars, but according to Professor Peter Struck of the University of Chicago it would be somewhere close to $15 billion USD (or $19.1 CAD) based on what he could buy during that time and how much it would cost now. While that conversion may be a give-or-take situation, it is enough of a difference from Jordan that we are able to assume he was the highest paid athlete by a long shot. Lamecus had enough in riches to feed the entire city of Rome for a year, or to fund the Roman Army for over two months.
Struck refers to Lamecus as the "best paid athlete of all time." Next time you scoff at a disgustingly large player signing, just remember that paying athletes in huge sums started a very, very long time ago.