This thread is about labor unions, which negotiate salaries. Sports people are almost universally not in this category - they usually have an agent to negotiate their individual salary.
If you're talking the SAG for actors and the like, median actor income is $46k, one of the lowest paid professions. That works out to $23/hr for fulltime work. You can get that at McDonalds in many places.
Try again.
Your claim about SAG is also wrong; SAG has plenty of pay caps too. For example, here [2] is one explained on their own site. They've always had them and likely always will. There's plenty more.
Unions extract higher pay by making a monopoly on labor (and US antitrust law had to carve out a special monopoly exception for them). This monopoly obtains higher wages for those in the union at the cost of those prevented from working by the union and by increased prices to the surrounding economy. These are all standard econ results.
[1] https://www.heritage.org/jobs-and-labor/commentary/should-un...
[2] https://www.sagaftra.org/important-notice-regarding-2022-com...