I think a lot depends on how much value you get out of considering residuals at all. Most of it after all is crystal ball stuff.
For me, and I suspect a lot of others, using a camper is a lifestyle choice. I cannot compare the "costs of holidays" because I do not in any case consider any alternatives to using my camper. I cannot compare camping costs to hotel costs because if I can live in my camper rather than a hotel room then I will.
The money has been tied up for a while, I no longer miss it and if I needed to sell the family jewels to survive the forthcoming recession then the camper will be the last jewel I will sell. The only time that residuals will be of concern is a) if I wished to trade in for similar or b
I pop my clogs in which case it is not my concern but my estate beneficiaries
Some years some things are worth more, in other years they are worth less, such is the way of the world.