The two games are worth $50 trade-in, so you traded the console for $125. It's worth at least $150, but if you sold it on amazon or eBay you would have ended up paying $15-20 in fees and frankly I hate selling heavy weight items that way because if you get in a dispute you'll usually end up losing at least the shipping cost even if the buyer is completely in the wrong.
So, basically if you were lucky with a local buyer you could have made a few bucks more, but I would say it was a fair deal and probably not worth the hassle to try to get more.