My girlfriend just traded her 2010 Nissan Sentra 2.0 S in for $11,000 .... pretty basic car she bought for $15,000 3 years ago. No way I could do that a with my 2012 SEL I got (msrp 24k, paid 20k).
I think people that don't buy and sell cars very often get way too fixated on the "trade in price" that the dealer "gives" you. The dealers do these trades hundreds of times per month and they are experts and manipulating you and your emotions. They often show large trade in values for your car, but screw you in the numbers on the new car, so their net is the same and you feel like you got a sweet deal. Now if you just wanted to bring your car in and sell it to them outright, without buying another car from them you'd be in for a rude awakening.