Hi 8thred, welcome to this forum.
The tub in question is at the "break" point in pricing for "used" stuff, that being 5 years. Less than 5 years usually means better price, more than 5 years usually means less. If the OEM warrantees are still running, it might be worth more.
Depending on demand for tubs in your area, I'd say $1,700 to $2,500 would be reasonable pricing, assuming excellent shape. Owners generally want MORE because of what they paid, but exceeding 50% of purchase price is not worth it (buy new).
Good Luck,
Drewski