I think it all depends on how much you use them, if a lot then the savings are enormous and must be factored in. If it's sat on the drive for 50 weeks of the year be prepared to lose money.
I wholly agree as the original question from the OP was whether caravans depreciated or not and not questioning how much you use one to consider if it's worth buying one.
Ours cost £600 three years ago. Don`t expect to get much for it in 3 years` time . . .or longer (we hope) but who knows? Might be a Collector`s Item by then . . .
------------- Peripheral people don`t have as much excitement but they sure live longer