Coaches generally make a certain base salary, but then get all sorts of money for endorsements, speaking engagements, shoe contracts for their team (yes, the coach picks the shoe company that will supply the team with their shoes, and the company pays him a buttload)... etc etc.
In effect, coaches at major college programs make $1 to $2 million per year.
It's not about how much their services are worth 'in their goodness' to society, it's about supply and demand. There's only one Steve Spurrier that's good enough to keep UF at the level they've been at since he's been there. That brings in cash to the school. He makes whatever the school thinks he's worth.