I suppose it's like anything, beauty is in the eye of the beholder...
I've transported plenty of these for customers over the years, and although I've never had the experience of driving one any distance, I too can't really see why they attract such high prices ?
If they were maybe £1-2k, then fair enough as a simple, old, basic camper.
But each to their own I suppose - I guess they must be easy to work on and simple mechanically.