My $.02 = if that 2006 is in like-new condition and comes with various accessories / camper gear, then it seems like a fair price. That number looks like a dealer lot price rather than a private sale, at least in my neck of the woods. Triguy is correct, like many big purchase items, prices can vary greatly depending on area.
I recently paid 2K less than that for an 06 27BHSS in very good condition with lots of accessories (from complete hitch setup to supply of toilet paper!). I paid the owner what a local dealer was going to pay him for it, same dealer he bought it from. Maybe I just got lucky!
Whatever you decide on, have fun!
2005 GMC 2500HD Duramax
2006 Wildwood 27BHSS