As you’ve no doubt heard, the NCAA is investigating Texas A&M quarterback Johnny Manziel for allegedly getting paid to sign hundreds of items -- photographs, footballs, etc. -- at the home of a Florida autograph broker.

Why does the NCAA care whether money changed hands? Because it’s against the association’s rules. And why is it against the association’s rules? The answer might surprise you. It’s not simply because the NCAA believes that it’s protecting some mythic ideal of amateurism. (Though that’s part of it.) The NCAA also believes that these rules are good for business. Allowing athletes to get paid would apparently diminish the appeal of college sports.

Guess what? Since the news of the NCAA investigation broke, the market has been flooded with tickets to Texas A&M’s Sept. 14 game against the University of Alabama. This must be because ticket holders don’t want to see a Heisman Trophy winner who might be considered unclean by the NCAA’s standards, right? Actually, it’s because they’re worried they won’t get to see Manziel at all because he’ll be serving an NCAA suspension. "Johnny Football" hasn’t even been found guilty of anything yet, but the mere prospect that he might is putting the lie to the NCAA’s claim that its rules enhance the competitiveness of college sport.

College athletes have been punished for all sorts of ridiculous “transgressions,” from taking discounts on tattoos to accepting endorsement money to pay for Olympic ski training, but this one really crystallizes the absurdity of the NCAA. The NCAA can sell as many Manziel jerseys as it wants -- until the association disabled the search function yesterday, you could just go to ShopNCAAsports.com and type in his name -- but if Manziel earns a dime from signing one, he’s in violation of NCAA rules. How, exactly, is that a reasonable policy?

I asked Eric Smallwood at Front Row Marketing to estimate what Manziel would be worth if he goes pro next year, as expected. Of course, there are all sorts of variables involved (including whether or not he loses any college eligibility this year), but Smallwood said he’d make between $4 million and $9 million for his first four-year contract, and an additional $3 million to $10 million a year in endorsement deals, depending on the size of the market of the team that drafts him.

Right now, though, Manziel is standing on the other side of the NCAA’s arbitrary line. For as long as he remains there, he is worth exactly nothing. He has zero earnings capacity. Or, rather, all of his earnings capacity is being channeled into Texas A&M and the NCAA. It's effectively an in-kind contribution to their bottom-lines. This is necessary, apparently, because if Manziel were to get even a small piece of the revenues that he’s generating, you’d stop watching college sports, right?

(Jonathan Mahler is a Bloomberg View columnist. Follow him on Twitter.)