Money and ego. Most of these guys want to be at the absolute top. Money is just a measure/surrogate for that. You don't get into their position and have that type of success without the desire to be seen as the absolute best.There is a point where money really isn't worth more than happiness. $7 million a year (probably more starting next year) to coach at your alma mater and have the resources to win a title is probably that point. Money always plays a role but I don't think it is the primary factor for most coaching moves at high-level P5 schools.