BYU pays less than Utah does for assistants. Possibly tied to that.
P5 money does make a big difference. BYU coaches are not poorly paid, just perhaps not paid as well as mid-level P5 schools pay.
Sitake was paid $500k on last contract, and rumor was has been offered an even sweeter deal to stay on as DC. Possibly $700k per is a good guess. BYU does not pay that.
BYU probably matches the lower end position guys just fine. It is the DC/OC that they might fall behind on.