Help-Dealer asked me for $. I traded car on new car. Dealer realized 9 days later

[NiceGuy]

they overpaid trade by $4800 What should I do here? Dealer called and said they made a mistake - incorrectly read a figure on the trade-in car sheet that caused them to overvalue trade by $4800. The price they appraised that car at was only about $1000 more than I thought I could get if I sold the car myself. I thought they were trying to make the deal work. The car I traded is in high demand so I figured the market prices are out of whack because of gas prices. In the meantime, the car I traded has already been sold to a wholesaler who sold the car.

Dealer is obviously desperate and offered to split the error with me. I would have to write them a check for $2,400 which is not what I planned since I financed part of the car.

What do you all recommend? Do they have any recourse?