KBB is just an average value of what your car might be worth when selling/trading it in/buying.
Just because someone says it's worth that much, doesn't mean you can get that much for it when selling it. It's only worth what someone is willing to pay.
I use both KBB.com and NADA books when buying or selling cars. I have found that NADA is much more accurate on actual value since those are usually the same books that dealers use. But I've never noticed that KBB is always $2000 off.
