To duplicate items, start by saving your main save on a USB device. Now create a new user on your console (there's no need to sign that account up for online access). Under your main account, start playing Diablo III. From the main menu, press the START button on the second controller, using the dummy account you just made. Using your primary account, gift any item or hand over any money that you wish to duplicate, so that the dummy account now possesses those goodies. Now quit the game and load your save from the USB device. Invite the dummy account to join your game, then have it hand over the items or money that you handed over to it a moment before. You have effectively duplicated that loot.