The "Black Book" is most every dealers bible when it comes to appraising a used car. A new book comes out every week, and is a compilation of several
"dealer auction" average prices for any given car in that area.
It's also regional, by that I mean, The prices a dealer has in their black book in Florida, will be different than one from the North East region.
When I had a used car lot here in the Akron area, and I purchased a vehicle at the auction for average Black Book value. I was almost guaranteed a profit by shipping it to Orlando Florida's dealer auction. Well that is, if I picked the right car that was currently popular down South.
Black Book had 4 pricing categories. Extra Clean, Clean, Average, and Rough. It also listed how much to add for most all popular options.