NIL is not the same as rev share. Schools can pay athletes directly via rev shares, and the total amount distributed is capped. NIL is not capped, nor is it directly from the school - it's through outside business entities.
My point to Calheel was that UNC can spend (around) 20.5 million / year, this year, on its athletes, and they are. They cannot spend more than that, without breaking guidelines/cheating, which I don't think they'd do. So, paying a coach 10 million / year or paying a coach $1 / year won't affect UNC's spending on players - schools can't spend more than the rev share cap. Of course, you can adjust the allocations of that 20.5 million, but that is a different argument, one which still would not be dependent on the coaching staff's price tag.