Note: This only works for items that stack/multiple items.

1.Move the items you want to duplicate to Junk (press Y). Move only one set of items. Go to a merchant and choose to Sell.

2.Sell the whole stack.

3.Go to Buy and then to Buyback. Purchase all but one of the items back.

4.Go back into Sell and to the Junk tab. Select the item stack. Press Y and, at almost the same time press A. The item will disappear from the list but a Sell prompt should appear. If not, repeat steps 3-4. Sell the whole stack. You will notice that the money you recieved for the items is twice the cost you sold them for.

5.Go back to Buy/Buyback and you will notice that the quantity of the items the merchant has are doubled. Repeat steps 3-4 as many times as you like for infinite gold and stacks of items up to 999