NADA is useless on an older coach other than as a negotiation tool, it is simply a depreciation curve, and not a good one at that as it lumps all coaches of a given general size and age range together.
Take for example the coach I own, a 28 ff 2002 Safari Trek with no slides on P32 chassis which had an original MSRP of $119,000 according to NADA it is worth $15,105, if you look up a much cheaper entry level 27 ft P32 Fleetwood flair from 1999 with an MSRP of $63,000 NADA says it is worth $15,105, the same is true of any other sub 30 ft P32 chassis motorhome built between 1997-2002.
As to real value, I spent 5 months shopping for my Trek within a 1,500 mile radius, the cheapest 01-02 model I found had a firm asking price of $15,500, it had not moved in 2 years as the brakes had failed driving up a mountain to its permanent camping spot, so at a minimum it needed to be towed 50 miles or have a mobile mechanic repair the brake failure. In the end I paid $20,500 for mine and consider myself lucky (asking price was $25,000). This is not to say that some don't sell for less, I looked at a Trek of the same model I ended up buying though a 1996 model, just a few miles from my house, asking was $6,900, I walked away when the seller was down to $4,900, it was a money pit, leaking roof, the list of stuff that did not work was much longer than the list of what did, paint was peeling, and the tires had been on it when the seller bought it 7 years before.