BYU reported sporting revenue of $72M, with 6% of that from broadcast partnership revenue. That's not football specific, it's all broadcast revenue.
Other portions of that $72M are ticket sales, memoribilia, WCC payouts (from NCAA tourney etc), but there's zero evidence to suggest BYU gets more from ESPN than what BYU is reporting they get from all broadcast partners.
And thus far, the biggest/only argument that's been said against it has been "dude, it's way more than that. Trust me. It's huuuuge". I guess I just trust what BYU publishes that has real-world implications and don't as same they're lying to us