Oh OK, so the trick there is finding suppliers where you can afford to sell for a bit under going rate at eBay. Going to be suprisingly difficult in my experience with the video game market. It's just a super tight margin product, generally speaking (although used/new-but-old games bought in bulk tend to have much better margins.)
Frank
Frank is spot on, this is a market that I do deal in and while you're theory is solid, it's not really practical at all. The margins are so tight on eBay that you already have to source in good volume to make a modest margin, so thinking that you could sell for even lower on your own site is nice, but near on impossible to pull off.
The only margin you would seriously have left would be the eBay fees you are no longer charged, and in the greater scheme of things, won't really give you much area to reduce your site prices much more than your eBay prices.
Definitely more money in second hand, but you really do have to understand the market, because while second hand can deliver good margins when bought at the right price, not all second hand titles sell well and sell for solid margins.