It's not a stupid question, I was taught many moons ago, If you don't ask, you'll never know.
Anyway, If you can't eye ball the camper and only have pictures and their word to go by, it is only worth what you are willing to pay for it.
As sellers we are all chasing top dollar for our item, as buys we don't want to pay more than we should or be ripped off.
Look at similar campers, Campers priced at the same dollar value.
What ever you are comfortable paying for it.