Good morning David -- and welcome to the Forums!
"True value" may be getting fairly specific. Your research will give you an idea of what similar units might sell for. This would come from having followed the classifieds here, at the VAC classifieds
-- and I think there are some over at airstream.com. Some general condition & pricing issues are at Price vs. Condition
This eBay offering looks to be from a dealer and they have a reserve price set. It's hard to say anything accurate about that. eBay auction prices can go crazy the last couple of hours, so expect this to go a fair amount higher than the current $7700 bid.
It might be hard to get an inspector on this short notice. Saturday mornings see a fair amount of Forums readers online but postings often die off at midday. Activity here has been very slow the last 48 hours. Have an alternate plan?