Rotten eggs sell for $2,000.

Have two controllers (works on Live too).

The host (Chris) starts the game, then sign in with 2nd profile (Sheeva), give the egg from Chris to Sheeva, then quit and save on both profiles.

Start the game with Chris then sign in with second profile or invite your buddy to the game.

Pass the egg from Sheeva to Chris. The host quits and saves the game.

Second player "DO NOT, I REPEAT, DO NOT SAVE THE GAME". Start the game and empty all eggs into your inventory.

Start the game and sign your 2nd profile (invite your buddy from Live).

When the game starts Sheeva should have all her eggs to give to Chris.

Repeat the process as desired. 45 eggs = $90,000.

The longer you do it the more money you will make.

Note: if you transfer all your eggs on the organize screen this will not work because the game saves itself at the beginning of every check point. Starting the game is considered a check point. It says saving... so you have to start the game in a safe spawn point, I use 5-3.