I'm just spitballing, but that tub NEW probably sold for around $9K +
The problem is gonna be the steroe. That's a $1500 option that you see no value in.
Considering that there's , no warrenty, delivery is extra, your gonna need new filters, and a 1500 accesory that you don't want, I don't see this being a viable option for you unless it's priced under 6500.00 Otherwise, you are better off buying a new tub fro arund 8K without the steroe, that has the warrenty delivery, new cover, new filters, etc.
What are they asking for it?
offer them $ 4,500 cash. Folks don't sell a 2 year old top of the line fully loaded hot tub for no reason. Why are the selling it?