The "trade in" value as reported by consumers is not particularly meaningful because that price is influenced by what is paid for the new car, especially when the trade is part of the negotiations on the purchase price of the new vehicle.

Instead try asking them to provide a written offer to buy your Crossfire outright, i.e., without you buying a car from them. You will not be offered $20K. Likely reasons they are able to offer you $20-21K in trade are that they want to move inventory and are making up the difference with their profit margin on the sale of the new vehicle and possibly on finance and other charges as well. Translation - they are giving you a "generous" trade value while you pay too much for the new vehicle.