Two other thoughts I have:
The schools themselves are creating enormous value, too. Georgia fans don’t buy tickets because Jake Fromm or Todd Gurley is playing here. They buy tickets and follow the program because of an emotional connection to the program (and for tickets, the quality of opponent who is coming to Athens). We didn’t see ticket demand or interest drop off any after Todd Gurley left.
The schools provide a platform, they provide training, nutrition, and healthcare also. Todd Gurley and Jake Fromm added value to Georgia. Georgia added value to Todd Gurley and Jake Fromm too. That often gets lost or overlooked.
The second thing is related to the first. True minor league professional football wouldn’t generate much interest because of the existing popularity of college football. You can even see that in baseball. LSU, Arkansas, Miss State will draw 8,000-10,000 fans for weekend games. You don’t see those kinds of crowds for minor league baseball, even in AAA. Heck, Arkansas will sell 5,000+ tickets for a Tuesday game against SE Missouri.
I think what you’d see from minor league professional football is that the money just wouldn’t be there. And I would argue that it would be harder for a player to create additional value in minor league professional football than he could in college.