In 2004 you could EASILY get a Altimar without stereo for $6,200. I had a quote for one with a Stereo for $7K in 2004. Using traditional "resale" value for Spa's, you should be able to get it for about 50% of that price. $3,500 would be VERY reasonable and that guy should be VERY happy to get it. In many cases, used spas go as cheaply as $500 or $600 but those are usually 10 years old or so. Offer him $3,000. If he balks, offer $3,500 as a "fair price" but I would not recommend paying any more than $4K for that particular tub. It IS a good one however and $4K would probably be a good deal.