Collectible Card Game Headquarters

How do you guys get the file size for the MWS scans so low? I'm trying to add the full black border to the cards, and it jumps the file size up so much if i do. Even in Photoshop, saving at compression of Medium yields a larger file size, and a crummier picture.

*EDIT*

NVM, I figured out that i could use "Save for Web and Devices" to get really great optimization.