Used RV Prices vs. NADA values
NADA is an average, not an absolute. That said, it is at least an 'indication' what a unit is worth. It probably would be used in determining a loan, and as such, paying above high retail, (or even high retail itself) would seem to be a poor idea.
From a dealer, I would plan to pay low/average retail or below. From a private party, I would pay no higher than 1/2 way between wholesale and average retail. Keep in mind that some dealers jack the prices way up, because some people will pay whatever is asked, and the rest will react to a 'bargain' of only 10% more than it is worth
Of course NADA values are based on typical units of that age, assuming they are in 'ready to sell' condition. If a unit is exceptionally nice, and/or has had extensive modifications of value, a higher price is sometimes warrented. And if it has excessive wear, defects or lack of preparation, the value goes down. These 'plusses or minusses' should be applied to the NADA value to get the 'real' value. But usually, you don't want to pay over 'retail', and smart people want to pay less than retail.
If you find one you like, make an offer less than NADA (I generally start at wholesale). The only acceptable response you should allow is 'Sold', 'No, but how about xxxx' or 'Get out'. Anything else is hot air and should be totally ignored. Have the NADA value handy in case he tries a sob story. Never ever raise your offer until they have come down some. And I would suggest not paying over retail unless the unit is truely spectacular. Oh, and don't forget -- if it is not written down and signed, no promise or claim made has any value at all.