Dealers here in FL know they are saving you tax on trade-in so they just deduct most of the savings from their offer.
Or, they just trot out the auction report showing your vehicle at rock bottom for any given mileage/condition and say "Why would I give you more for yours than for one I could buy at auction, cleaned up, and on 30 day terms"
Convenience and financing is what they have to offer, at an expected and sometimes deserved profit.