Boise State gets about $3M, so I think it's safe to assume that BYU could get a similar number from the MWC or AAC. You account for a bit of additional media rights (such as for radio or BYUTV) that BYU would still be getting on top of that $3M from the MWC, and I think you're getting pretty close to the $1M difference.
This all depends on how much BYU could get in a conference (would it get a bump like Boise?), and how much BYU would be getting in its next Indy deal or its next conference deal, because those numbers are about to be changing.