My feeling is that for 20+ year old motorhomes the averages assume a pretty horrible condition. And let's face it, most motorhomes that old are in pretty sad shape.
So when you sell a 1991 Class A like I did last year, in great shape, with appliances, a/c, etc, that had been replaced in the last 3-6 years, tires only a couple years old, etc., the lowest offer I got (and it was a thousand less than what I sold it for) was twice NADA.
The Green Machine -- 2000 Mountain High Coachworks Summit (Spartan chassis / Cummins ISC)
...and F-Troop: Fearghus, Fiona, and Frankie (Cairn Terriers)