Few sellers will list the price at their rock bottom dollar. Most buyers try to haggle price down, so the listed price is usually a starting point, but don't expect a huge discount.
The value is all dependent on the condition and what upgrades have been done.
If you were to have a shop install solar, for example, you would spend $2,000 possibly (way too much), so if you want a solar upgrade then consider that as a value. ( I can do same upgrade for $300 DIY).
What else is upgraded? mattress? fridge? interior lighting? inverter? tie down mounts included? high end tires or WDH for camper trailer shoppers?
There is a myriad of things that can be upgraded that add thousands to the value.
For a camper that is bone stock, I would not consider paying too much.
I would not look at something like NADA or Blue book for pricing, that is Pricing For Dummies and can be so far off reality.
Shop the internet and see what similar units are priced at, watch enough to see what they sell for (big difference).