I mentioned this on another topic, but the first time that I ever traded in something I was a little kid that didn't know any better—I traded my complete NES for
this and
this, which amounted to essentially $20 or so. I was, in the simplest of terms, taken advantage of. After leaving the store and getting in the car I realized what I had done and remember regretting the trade on the way home. It was a learning experience.
Then there was this one time many years ago where I was at a GameStop and witnessed a trade going on where this guy brought in a bunch of games and got something like $50 and some change for it all. All of the games were complete, mostly for PS1, and one of the games, if memory serves, was Final Fantasy VII.
Overall, I don't trade even if my life depended on it, and whatever I end up selling is either because it's a double, doesn't interest me at all, or just outright doesn't belong in my collection.