Airstreams cost because of the volume, construction, quality and pride of ownership factor.
They are very high priced and would not be so if they were not worth it in the eyes of their owners.
Considering you could buy two or even three standard TTs for the price of an Airstream and a 20 year old AS is just reaching puberty in TT world, says a lot.
We looked at them briefly, The DW did not like the shape, I want a slide and neither of us wanted to spend that much. None of that has anything to do with the value of an Airstream.
To put it in perspective, if I won a multi-million dollar lottery, Ferrari might just make their first pickup truck. :) Till then its my F-150.
Safe travels