Value and Cost are often quite different things with old cars/vans/bikes. VW prices are quite easy to find out as there are so many of them and they change hands frequently. Valuing Commers is much harder. I looked at every single van I could find for sale over a 3 month period - which was a total of 4 vans! All of which needed work.
How much more should an early (tax exempt) autosleeper be worth over a late coach built? Originality? Upgrades? Nice interior? New MOT?
A bit of wielding and a few panels (£500-£1k), a respray at £1-2k, a set of tyres (£300), sort the mechanics out (£300), tart up the interior (£200)…
Multiply this by how much you think your own time is worth and the costs of travelling all around the country looking at vans weekend after weekend.
Assuming you’re not planning on buying and selling the vans to make a profit - and your alternative is buying a VW then there is a lot to be said for buying a van that you can use straight away and you like.
If you know how much they paid for it, and they’ve had it hanging around for a while try putting in a low offer. You never know.