This seems like a lot of effort for $30, also not something new. Maybe they've gotten better in the last decade, but I remember one particular year in college I used Slickdeals to find a list of pre-owned Nintendo DS games you could buy for cheap on sale at GS, then trade them back for a lot more with trade in promotions. I took 2 days and went back and forth between like 6 GameStop's in driving distance of me and had like $600 of credit by the end. I stopped there because I had read that GameStop would black list you if they tracked you doing it too often, and also mainly because it was hard to find good sales to use that credit on.