A quick look in RV Trader reveals the following:
A new 2014 22' Airstream Sport has an MSRP of $50K or so.
A used 2008 is being offered at $35K ($15K less/30% less than new)
I couldn't find any comparable units that were 10 years old, however, a unit that has lost 30% of its value in 6 years doesn't indicate to me that Airstreams have high resale values as indicated by some posters. Sure, you may buy a highly depreciated used Airstream and keep it for 10 years and lose very little money, but the same thing can be said of practically any type of RV or brand.
It depends on what the 2014 was actually sold for, then resold for. MSRP is anything the dealer wants it to be. It is not necessarily what a customer pays.
Check out a Lance, or Arctic Fox, or Shadow Crusier, or Rockwood, or whatever and see what the spread is new/used. Then you will get some comparative data. From what I have seen box trailers depreciate about ten percent a year so at the five year mark they are worth about half of new. Hopefully the owner never paid MSRP or the depreciation hit could be bigger each month that the payments are to the bank. Maintenance and condition also dictate a lot of the used value.