He's already earning in the $3M range and the new contract that will come with the B12 will pay him the average of the B12 coaches.

Current Big 12 coach salaries (not including Oklahoma and Texas)

Mike Gundy (Ok St) $4.25M
Matt Campbell (Iowa St) $4M
Neal Brown (WVU) $3.98M
Chris Klieman (K State) $2.82M
Lance Leipold (Kansas) $2.75M
No coach at Texas Tech or TCU and Baylor info not available.

So that's a $3.56M average. Given BYU's history, I'd expect them to come in slightly below that average so in the $3M to $3.5M range.

If someone comes in at $6M, that's a difference of $15M over the life of the deal. I like BYU, but maybe not as much as I'd appreciate an extra $15M