Running some quick numbers on KBB, your car is valued from 11-13k and a 03 Cobra is 21-25k. There are tons of variables here (mileage, trade in versus private sale, condition, ect), so this is just a reference. I have never seen a 03/04 Cobra in my area going for less than 24k.
I know what you mean. 50-60K miles people around detroit, MI are asking 24-25, while people with 1K-20K stock and modded, are asking 30+. I remember in the Fall of 2004, Russ Milne Ford had a handful maybe four or six 2003 or 2004 Cobras brand new for 26K. That is when I should have bought one. But I was impatient and supercharged mine eariler that spring. People are crazy.