In a good year, slightly over 40,000 Class A motor homes are sold in the U.S. Many less in a bad year. That includes lengths from 27' to 45', gas and diesel, and hundreds of various models from a large number of manufacturers. It would be easy to see that in a given year, less than a handful of a particular model may be sold new and subsequently many years may go by without a used sale of a particular model.
Considering those facts, it would be difficult to think anyone could publish a "book value" pertinent to real world value without a range of +/- at least ten percent with any accuracy. NADA values are simply a depreciation algorithm based on motor homes in general. It does not take into account popularity of model, condition, wear and tear, popular and unpopular configurations and multiple other factors.
The potential end user of a used unit is looking for a model that aesthetically, meets their needs and budget, appears to be mechanically correct, is currently available, and fits within their budget. It would be a "fools errand" to seriously factor in the desire to buy a unit for less than some mythical value printed in a book most often read to them by a banker who most likely has never been in a Class A in their life.
The educated buyer will spend far more time looking at and comparing units in their budget range as to how well they "work" for their own purposes and desires. They will spend time and money determining that the unit is in "good condition" and will not turn into a money pit after the purchase. Six months down the road, the 10% variance in theoretical value will be long forgotten when compared to the ownership experience so far.
