maybe $500...if it froze to the point of cracking the pump housing, it could potentially have more in-foam leaks in which case it's landfill material unless you can find a DIY'er who wouldn't mind a "project"
Exactly this. If the pump housing cracked, I would bet that there are other leaks, which are probably buried in the foam and a nightmare to get to. I hate to say, but you probably have a worthless hot tub at this point. Less than worthless because you have to pay someone to dispose of it.
I tell people all the time, do not buy a used hot tub unless you see it up and running. People will say "it worked fine when we last had it up and running a year or 2 ago". The problem is that they didn't evacuate the water from the plumbing, it froze, and there are 5 leaks that are difficult to fix.