Many of the comments here are seem to be along the lines of "I don't like them", but that wasn't the question. Obviously the people who DO buy them must like them, whether because of their mystique or actual features and construction. Airstreams are designed and built with a spare no expense attitude, resulting in a choice of materials, components, chassis and running gear that puts it well above typical travel trailers costing 1/4 to 1/2 as much. If you look at an Airstream and only see a trailer with a high price tag, my advice is Do Not Buy.
Even the little Sport model has aircraft-grade riveted aluminum siding, a robust chassis, Ultraleather upholstery throughout, top quality flooring and paneling, Moen plumbing fixtures, stainless steel sinks, probelelss (external sensor) tank monitors, heated underbelly, 80W solar system, AGM battery, rear camera system, and other nice features. PLUS a 3 year warranty and 3 years of Coach-Net roadside service included. Larger models have inverters as standard equipment, big Samsung tvs, surround system, and similar high end amenities.
If you look at other trailers with similar high end construction and amenities, I think you will find the prices similar to the Airstream. Here are a few:
https://land.olivertraveltrailers.com/fiberglass/travel-trailers-1/
https://horizonsrv.com/
http://www.travelunits.com/