BamaCoug and I don't always agree exactly on everything, but I have pretty good confidence in his numbers and processes.
I will say it's hard for me to believe that ESPN values BYU at $90M (in the Big 12). If that's downplaying and insulting BYU, I guess you can think that.
But the SEC is getting a deal worth $960M/yr for 14 teams, meaning the average SEC team has value (and media right payout) of $68.6M. If BYU is really worth $90M (and probably closer to $100M with SEC opponents in the schedule), then I can't imagine the SEC wouldn't be interested in increasing their per year per team payout by $2M by adding BYU.
Similar story for the B1G. Right now they're at $75M/team/yr on average. If BYU is really worth $90M+ then the talk would be about the B1G adding BYU, not about them adding Oregon and Washington.
That's not saying that BYU is a bad program or doesn't have value... It's just saying that other conferences (which are presumably interested in making money) aren't lining up to treat BYU like someone who would add $90M to 100M to a media deal. Which makes me skeptical of that.