I had previously attempted this at another GameStop, but I made the mistake of leaving my KFP/LIJ box sealed, so I couldn't trade it in anymore there.
So I hauled ass to the one at the mall down the street, and was a little unnerved to find that the tag on B-OS read $29.99 instead of $19.99 like at the one I was just at. What put a smile back on my face was the clerk telling me that the game was really $20.
All in all, I sold a pack-in set of games that I didn't care for, and got a soon-to-be-rare Treasure title without expending a single real penny. Suckers.
All I can say about B-OS is: MORE. FUCKING. DAKKA. It's kicking loads of ass, and it's kicking mine's too--what other game has a tutorial mode where you can DIE? And with 160 stages (and room for 24 customs), this is gonna get a lot of play time for a $20 game. It's joined the list of bargin games that are most definitely not bargin bin trash.
Space Invaders Extreme > $20
Star Soldier R > $8
Gradius Gaiden (which is > V, which in turn is >>> III SNES) > $30
On the darker side, Ketsui Death Label is not looking so hot. Broken scoring + 20 lives = lose.