Snomas,
This is a seller's market for RV's. I've heard of people of selling their RV's for what they paid NEW for them 2 years ago. That's unheard of!!! I don't think the NADA numbers mean much for anyone selling who has a pulse on the current market.
I think things will get much better in a year or so, hopefully, when the many people who recently bought RV's for the first time realize they're a lot of work, and not any cheaper than other types of vacations. So if you can wait this out, it'll work in your favor. Remember that if you DO pay their asking price and the market softens up dramatically in a year and you need to sell it, you might have to take a substantial loss by selling it in the NADA range.
You're the buyer, make a fair offer with the proverbial "cash in hand". It's up to the seller to accept it or not. Be prepared to walk away. If the rig is still for sale a week or so later, try again.
Good Luck,
~Rick