Hey Tom,
To offer you some info on what we just paid for one... We just bought ours for $6k in February on Craigslist, it was basically in original condition, and native to colorado, the toilet had been replaced, otherwise was in "used" original condition.
The floors were in original condition with after market carpet that we removed (wood was solid and not punky at all)... the water heater (as we found out post purchase) had corroded out...
My folks live in Michigan, and found that the same trailer was selling for about the same there, however with typical midwest rot to the floors..
Hope this helps.. additionally, we found this website that was helpful, hard to say about it's accuracy, but it justified it in our minds....
Price vs. Condition - Airstream Values