keep in mind, sometimes kbb or other price market value doesn't really pertain to the car/motorcycle/boat/etc..etc.. that you are trying to buy.
The so call "blue book" is only a guild to help you understand what the value the marketing is going for just a basic product. But if the product you are trying to buy is more than just a basic product on the market, the value for that product is higher. This is where you have to do your research, understand what you are buying and go from there if the price is right for you.
Don't always assume that the "blue book" is what you need to follow. Do your research and learn about the trade.