If you had given him sticker on the Boss he had the extra $$$ to throw at you for the trade. Some dealer give you more on the trade and less off the sticker. I shop the new car price leaving trade in if I have one off the table. Once I know what is a fair price for the car I shop my trade. Trust me the dealer knew the value of your Corvette
I'm not so sure of that, that dealer, (race red car) was pretty rural, (lot was all trucks).
I checked E-Bay, there wasn't a COMPLETED LISTING for an '04 Corvette anywhere near 20K, they just weren't selling. So if he couldn't retail it (which I doubt in his area) he would have to wholesale, and take a hit. The other dealer, outside of DC who gave me $18K, had the market. I know I made out good, the Boss was $4500 under MSRP, the trade fair. The Corvette sat on his lot for two months, he was re-selling the car for $21,500. Which leads me to believe the first dealer was way high in his offer of $20K.