I'd argue that for revenue-generating sports, the money is definitely there. For example, most (maybe all) P5 programs could afford to pay their football players; many could also pay their basketball players based solely on what their basketball programs bring in.

But pretty much every other sport is parasitic to football and basketball. And, because of Title IX, football and basketball require at least some of those other sports in order to survive. Title IX wouldn't allow for payment of football players if an equal number of female athletes weren't also paid, and that puts universities in a bind. They theoretically have only two options:

1) Pare down their athletic department to its leanest possible state, with only football, men's basketball, and a sufficient number of women's sports to balance out the numbers. In this case, all players would be paid.

2) Continue with the status quo; use football and basketball revenues to fund a variety of less-known or less-appreciated sports. This requires much thinner margins and often puts athletic departments at risk of running in the red—and it doesn't leave money for paying athletes (at least, not paying them much more than they're already being paid). However, this solution arguably provides a better experience for students, student-athletes, and alumni because the athletic department is well-rounded; there are campus sporting events all year long; it keeps the school's name in the news; and ultimately, it just feels better than only fielding one or two men's teams and enough token women's teams to satisfy Title IX.