A small tweak for Blizzard's World of Warcraft is causing big effects for subscribers and the massively multiplayer online game's economy. Blizzard highlighted the in-game update in a video released Monday. As part of the tweak, WoW Tokens -- an item that can be purchased with actual money or in-game gold -- can now be used to add money to a user's Battle.net Previously, WoW Tokens could be redeemed to add an additional 30 days on a user's subscription time or sold for gold on the game's auction market. While the tweak has only been in effect for one day, it's caused massive global spikes and fluctuations in gold prices for World of Warcraft subscribers.