Today, fully fitted out will set you back around 45 grand. 3 years down the line you'll have lost 20. If it's a hassle free bus people want in as new condition, then it's quite easy to build and spec your own 1970s bus for 20 to 25 grand all in, including the purchase of the bus and paying professionals to do most of the work for you. That would include a flat four Subaru 2 litre (140bhp) or 2.5 (170bhp) engine, which is far better than the 1.4 VW Polo (80bhp) fitted to new Danburies. Sure, you won't make any immediate cash from your 20 to 25k investment into your 1970s bus, but in 3 years time you wouldn't have lost 20 grand. In fact, you wouldn't have lost anything at all, because it'd never be worth less than what you've spent. So I don't get it. Why would someone buy a new Danbury and throw 20 grand down the pan over 3 years?
Because they're new, have a 3 year warranty, finance, spec'd as you choose, convenience? May make no financial sense but buying a car never does.