The old popular example was the http://www.wowhead.com/item=47257. This item differed on my server from a high of 6k to a low of about 3k. When the price was down at 3k, I would buy a few of these and just wait a week. Throughout the week, I would put in trade and the auction house that I wanted 6k for it. I would then immediately go onto an alt and say that I only wanted 5200g. Sometimes, I would get the 5200g and be a very happy man, other times it would take more patience. However, almost always, by the end of the week, the other sellers had reposted for around what I wanted. This gave me a huge advantage. Now, the price ceiling was no longer 3k on the auction house, but 5k. I could now easily sell the few I bought for 4 or 4.5k, which is a huge 50% profit from the 3k I originally invested.
Guide to Obtaining and Selling the WoW Token Buying and selling the WoW Token, which allows players to buy game time with gold, or make extra gold by selling the token on the Auction House. What is Blizzard (Battle.net) Balance Overview of Blizzard (Battle.net) Balance, a currency used to buy Blizzard Entertainment products including World of Warcraft character services. How to Purchase World of Warcraft Game Time The cost of a WoW game time subscription, how to acquire a subscription, gift one, and cancel it, as well as how to play WoW for free.