You'll need to reach Chapter 5 in order to take advantage of this glitch. At this point in game, ensure that you have less than 60,000 Gold. Accept the Travelling Merchant quest, and save your game.
Then travel from town to town until you locate the Merchant; you need to find him within 15 game days, if you can't locate him in time just reload your game.
Attempt to purchase the item he offers, and even though he'll say you won't have enough for the transaction (because you should have less than 60,000 Gold) you will acquire the item AND 99,999,999 Gold in the process!