Its definitely not a lucrative career, but I can see how people can make a few bucks. In business we have a term ROI, return on investment. These guys haggle, rip people off (some do), work their way up to better items then cash out.. Or they buy keys and hope for an unusual.. (they referring to frequent traders). They aren't going to make a good ROI, they spend hours a day doing this and their $$ per hour isn't very high.
I stopped trading because I know alot of them (who i knew well) would even try to run me (a colleague, friend etc) for $$... It just got pathetic.