Kennedy,
While Airstream's cost a little more in the entry fee department they typically last much longer than the standard box trailer. They will outlast the payments, something not all RV manufacturers can say. About 75 percent of all Airstreams built since 1935 are still on the road. The money going in will buy a product that will outlast you, your kids and perhaps their kids. So, they are not more expensive in the long term. Airstream does not use rubber roofs that need to be replaced in 12-15 years, no gel or filon sides to delaminate, and are proven wind resistance cheaters with the iconic rounded front and rear. Nothing on the road speaks RV better than the shape and name of an Airstream. Some models incorporate slideouts and the 34 foot PanAmerica is a triple axle toy hauler. Not that RV's are investments but it is doubtful there is a better long term ownership RV investment on the road.
There are also non monetary benefits to Airstream ownership. Many campgrounds with the ten year rule tend to forget that rule if an Airstream pulls up. There is almost no easily discernable significant difference between a new Airstream and one well kept twenty years old one. So, they don't care. Airstreams are in a league of their own. You either like them or you don't. Sort of like Harleys.