The logic is say the old coach is paid $3M/yr; new coach $7M - where does the $4M difference come from - a $4M booster donation most likely. Cost to booster of $4M less the tax deduction impact; so maybe $2.5M net cost and lower taxes of $1.5M. Now this wealthy booster may have an alternative minimum tax that largely eliminates the benefit; but that is the logic.