http://imgur.com/a/7NKei
Doing this shit should actually be restricted through in-game system. Now, I'm not an economist IRL but I'm pretty sure that if you open up a shop or business there is a law preventing you from setting your prices absurdly low, because you cut out the competition, and in order for the competition to follow you, they should all drop their prices so low that the entire market value of the product or service gets f***ed.
I know I shouldn't be drawing parallels to real life economy in a game but I'd like to see undercutting greatly restricted on the Auction House, and if you want to sell something for 50% of the price like the moron over here, just use trade chat instead. Also worth mentioning are the individuals that, using the Auctionator addon, then add up to the misfortune by undercutting the troll price itself and ruining the prices even further.
I have NOTHING against undercutting for small amounts in order for your item to be sold first, I did it, you did it, everyone did it. As long as the average market price remains the same. Destroying other people's chances at earning decent money with the effort they put in by leveling their crafting skills and gaining the recipes, is pathetic.