I have taken a number of cars to carmax and have always gotten a little over kBB trade-in.

Few months ago they offered $15k for my 05 roadster with 18k miles.

Also took an '11 Toyota Sienna that the local Volvo dealer offered $24 in trade on a '12 Volvo S60. Carmax offered $28.

Yes, their buy and sell prices can be beet if you are a good negotiator. Are you expecting to get more than wholesale?