What is up with the Dodge Dealers???

My son just bought a "used" 09 Black R/T. it had 6K miles. The PO done some upgrades to it before he could no longer make the payments and traded it for an Avenger R/T. the PO put after market exhaust, wheels\tires, KN cold air intake and "chip". The dealer had $40K on the car. We talked to the sales guy, I told him 40k was to much for a used car. Being a smart a$$ he called the new dealer and asked how much for a new one, the price was $46K. So me being a smarta$$ told him that was way to much for a fu_king car. So needless to say the sales guy gave my son $12K for his 01 Chebby blazer. So he gave $32k for the car with 6k miles.
My son is in the Army and just drove his Challenger to Ft Bilss, TX from KY and got 25mpg crusing 10mph over the speed. I hear that TX open road is 70mph. Dealers that want to sell cars just need to be told what the car is worth and they dropped $8k off, easy for them when priced to high and they know it.