I was thinking sunk cost as well, but I don't know if it applies here. Can you call it sunk cost if the thinking is "if I get through this day, it's one less day to the pay off" as opposed to "I've already put so much effort to this, I can't leave now!"?

It's actually better for leaving because the cash is paid monthly in the first couple years, and you don't have to wait for the next quarter or half or whatnot if you decide you want to leave.

That's the opposite of a sunk cost. That's a pending reward.