It's not a scam. And NEVER trade in a car. Spend a day thoroughly cleaning it inside and out, take good pictures and videos and post a good classified ad and you make much more than trading it in.
My mother was just offered $4500 on a trade for her civic(so $5085 equivalent once tax savings factored in). I did the above and within a few days I sold it for $7000. I could have gotten even more but she was happy enough with that and took the money on the spot. A day spent cleaning and posting an ad earned her $2000 more, simple as that.
Did the same with my gf's car a few months back. She was offered $1500 for her car on a trade and we sold it privately for $3500.