This exploit is patched in version 1.03. You have the ability to open up all the chests over and over again to sell for money. The key is to not open up any brown chests in single player mode.
1. You first want to party up with someone first and head into the Hollow area.
2. Start multiplayer and load up your team with different characters.
3. Teleport to the various areas to pick up the brown chests. All of the brown chests respawn as long as you have not opened them up in single player before.
After you collect all the chests, you can either die or exploit the unlimited teleport crystal from Asuna’s inventory.
Note: You can enter any area through multiplayer mode as long as they are not locked via story.