Leave it up to you to bring up the only other exploitative system in the country that rivals revenue college sports. The medical residency system. It's an extremely exploitative system. Thats exactly another place where people are paid way below their market values. And they only get away because they had congress sign an iron clad law special exemption in place that protects the match system and leaves residents no room to maneuver.
Under ideal market conditions (which rarely happens), As long as there is no or minimal restrictions on entry/exit, and ideally there are multiple buyers and sellers, and each participant is free to negotiate as they please, you end up close to the market value. Medical Residents, who are already doctors by the way, don't have that. There is iron-clad match system that matches them to a hospital, and strong contract that absolutely binds them to that hospital. That's why resident abuse is so rife. As a surgical resident, I was comfortably the least paid employee in the entire hospital on a per hour bases. A resident is not free to choose from multiple options and negotiate what's best for himself or herself. if you remove the artificial barriers, and left it a true free market. I guarantee you medical residents (some specialty more than others), easily get 2 to 3x if not more than what they are currently being paid.