Hello donnalynn -- Welcome to the forums.
The Price vs Condition
vintage website doesn't cover either trailers that new or the very limited run of 5th wheels. It does give you an idea of factors involved in pricing. You might monitor want-ads in the classifieds at this forum, the Vintage Airstream Club
or I think www.airstream.com
even has a classifieds area. At least look at similar length and year Airstreams & Argosy trailers to see what sellers think they're worth -- not always what they'll sell for of course.