I think what I've seen is leaving out half of the analysis. The way I see it, FOX/ESPN are paying for inventory, so it comes down to the relative value of the games they would be picking up by adding certain teams.

ESPN already has BYU home games in its inventory through the current deal with BYU.

If BYU joined the B12, ESPN isn’t getting new inventory from BYU, it’s just paying a lot more for the rights to those home games than it currently is (granted, it’s not necessarily apples to apples, since current BYU home games maybe aren’t as big a draw as regular games against B12 opponents would be, but I tend to think—and we’re starting to see with 2016’s schedule—that if independence continued, the BYU home game inventory improves).

Having said that, the analysis can’t be done in a vacuum either, since if the B12 expands, without BYU, it is presumably (for argument’s sake) adding inventory from 2 new teams that it doesn’t currently own. The question at that point becomes (assuming 2 teams have to be added and we’re just deciding which two) whether ESPN values the price it would be paying per game for those teams’ games more or less than it currently values BYU’s games.

In other words, ESPN is getting a good deal on BYU games at the moment, and no longer would be getting as good a deal on those games if BYU joined the B12, but still may be better off adding BYU if the alternative expansion candidates are even less of a value proposition.