NADA "retail" & "wholesale" values are just estimates, but typically they are about 20 to 30% too high. The on line version has only the two figures, but the printed book has a third set of figures that reflect "trade-in" value, which may be closer to the actual market value.
NADA's estimates on RV's are not based on actual sales of similar units, but from generic sales cross referenced to original MSRP, which are also typically excessive. New RV's are typically discounted significantly, sometimes 30% or more. NADA's estimates for cars are computed completely differently.
But, bottom line this is the only good reference available to use as a starting point. It can give you an idea of where you're at and what to look for. If you're looking for something more accurate, try PPL's web site. They post the prices their consignment units sold for. While this doesn't tell adjust for condition or options, it is probably more reliable as a value guide. Good luck.
Holiday Rambler Navigator DP, Hummer, and Honda VT1100C Shadow