I generally consider a hot tub to lose 30-40% value in its first year, so based on that, it would be worth $7,200 - $8,400. Every market varies. The warranty only applies to the original owner, that is how this industry is. You can absolutely ask $10,000, but I doubt you will get it. I always advise my customers that if they are looking at a used hot tub to make sure it is filled, up to temperature, and everything works, otherwise it is worth nothing. It will also cost somewhere between $300-$700 (or whatever the going rate is around you) to move the hot tub.
I agree with hottubguy, if you really like the hot tub and would be getting the same one again, put yours in storage. Otherwise, you are going to take a big hit financially.