I have mixed feelings on New vs. Used.
I'm now on my second "used/Vintage" trailer. I thoroughly enjoy transforming a trailer that was down and out in to something functional and new-er. However, I would also enjoy just getting out there and using an Airstream instead of spending every extra minute I have working on it.
The trade off is that when I get done refurbishing/modernizing my trailer, I will have exactly what I want, and will know every inch of it and how it was constructed. No surprises when I am out on the road and something goes wrong. I should be able to do most any repair myself. (other than the AC or some electronic appliance component failing)
As for cost... Well, I cannot afford a new one, but if you factor in the minimum wage I could pay myself while working on my trailer, and the cost of materials... I could have purchased a new one, but it would not be exactly what I wanted.
Vintage Airstreams and simply redoing one that isn't the way you want it, is as much a part of the Airstream Culture as is the person that travels constantly in their new/newer trailer. There are many ways to enjoy an Airstream.