Unfortunately im finding that jimmy_salehoo is completely correct in the profit margins on new games.
if you want to buy and sell video games its best to tap into the used video game market. garage sales, placing an ad in your local paper, and other places is the best way to get in touch with these items.
I have been doing this and have been making HUGE profit margins. I recently bought a box of stuff for 1 dollar and sold two of the items in the box for 58.50 combined. GOODLUCK