Is NADA a good reference for TCs?

It is not going to be accurate as NADA is based on actual sales by area and the number of campers of a given model that are sold. I found also that the price was in part a matter of supply and demand. Campers for sale in major cities had more available buyers and sold for a higher price and were on the market a lot less time. Older campers, i.e. pre 2000 models are much less in demand and it is a buyers market.

Condition also varies widely as some people take a lot of care with their campers and may even store them indoors and others trash them and do not do the necessary maintenance.