Although I am sure that some kids parent actually flip the bill, I would be shocked if the majority of the money isn't provided by the top recruiting colleges from the major conferences. I don't know which colleges, but I could take some guesses. You can't spell Scandal without AL in it
Most have endowments and donation from alumni and churches to help pay for tuition for needy (good athletes) students. What is not covered by those funds is made up from those parents who can pay. Tuition is never equal to the cost to educate one student. They always add in a little extra to get more out of the one who can afford to pay more.