Auctions are also one of the best money-sinks in the game.
Each faction has its own Auction House, and the two factions share Auction Houses in neutral territory. You can find or sell weapons, armor, trade goods, recipes and reagents. The Auction House (abbreviated as AH) is a wonderful place to find what you need or even make some money for yourself.
The Auction House is notorious for being ridiculously overpriced at times and at others being a really handy tool to get great items.