Dealers and a lot of priv buyers use the KBB to hold open doors. Try taking a vehicle to a lot and getting a price on it as a sale only.
We sold a few vehicles privately in the last 3 years (96 Escort, 92 Plymouth van, 78 Bronco) and had to wait months before we got a decent offer for each from private buyers.
A prev poster said the same; he never paid above dealer trade/or wholesale, so go by that at least when using KBB, NADA, or Edmunds' values.