Garrett is a sunken cost. The money is already spent. The issue has absolutely zero to do with what he is owed moving forward. Zero. The issue is paying his replacement as well. That is what would hold him back. If Sean Payton said he would coach for free, do you think what Garrett is owed would matter? No.
Now does he care about the $24 million+ a new coaches salary? That we can't answer. I don't know why he would though. He's a billionaire in his 80's with a franchise QB on his last hoorah. He will never spend the wealth he's accumulated. If it costs him $24 million cash and another $30 million over 5 years to get him another ring, why would he care? Romo is on the back 9 of his career. Jerry could be teeing off on 18. If a SB is really what matters to him, the cost won't matter. Odds are, he's not going to be capable of running the team by the time another franchise QB is found anyways.