Here's a question I can handle.... (from my handle, you could guess)...
KBB gets its money from 2 places.
Biggest one is from insurance companies that purchase values. Insurance companies use those values to set your rates (primarily for cars, not motorcycles). Let's see.... is it in the insurance company's interest to set those values high, or low?
Second is is from auto dealers who purchase window stickers for used cars that show "KBB price" and "our price". Now, if KBB truly reflected the market, it wouldn't be mathematically possible for dealers to consistently price below KBB, would it? KBB prices are normally way high, which enables dealers to show "our price" is a great deal.
NADA values can be closer, but still should not be considered a real market value. NADA's primary data source is monthly surveys that dealers send in. I've been in the business for 34 years, and I've never seen a dealer return a survey yet. The sampling percentage must be very low.
The only guides that are very accurate are auction results, which are not available to the public. Those reflect actual transactions with a willing buyer and seller, and are as recent as yesterday.