The ACC schools hold all the cards in the negotiation. If Clemson is pulling out $33 million a year from the ACC, and would get $115 million from the Big 10 or SEC, then it would be worth it for Clemson to leave if the ACC would get $82 million a year from the Big 10. Is Clemson willing to pay $82 million (and growing) per year until 2037 or whenever the ACC GOR ends? That would be the opening position for me if I was Wake Forest's President.
I'm not so sure. There are two factors to consider.
First, the current withdrawal fee to leave the ACC is probably about $100 million. Fortunately, withdrawal fees have been negotiated down in the past. So, maybe an exiting ACC school could get that number cut in half?
The second and far bigger issue is the grant of rights. If your example school, Clemson, left the ACC without regaining those rights, Disney would still be writing checks to the ACC for the broadcast of all Tigers' home games. I suppose Clemson theoretically could agree to play all their games on the road (or at a neutral site) for their first decade in a new conference as a workaround. But that isn't going to happen. An exiting member simply must regain their broadcast rights before leaving.
The first way to regain those rights is through negotiation. The average payout per school that the ACC will receive from Disney over the next 13 years is worth what $300 to $400 million? But Clemson is really worth more than that to ACC. Why? Because ESPN is likely going to revise their contract with the ACC down if the Tigers leave. There just isn't much incentive for the ACC to negotiate.
Another way out is to dissolve the conference so that the GOR is nullified. It currently requires a supermajority vote to dissolve the ACC. I'm unsure what number constitutes a supermajority, but Clemson would need a bunch of schools to have new homes lined up for this to work.
Probably the last mechanism is legal. Clemson's lawyers would need to find a flaw in the agreement that would allow a school to win a court case.