What price would you be prepared to pay today in 2007 for a guards van you know only cost $500 in 1989??????
Yeh, let talk philisophically!
If I wanted a van like those and there were none available, I would pay the asking price or a lesser negotiated price if I found one.
If the seller is in no hurry to sell, I might have to pay more. If the seller is desperate, I leave my 2 phone numbers and walk away.
I'm sure of the extent, but the work done inside the van, altering it, might save me doing it and the value changes.
Also the condition and possible restoration costs are to be considered.
The vans may not be what an enthousiast is looking for if modified too much.
It's too hard to value in respect of apreciation or depreciation without factoring so many variables.