Over the years we've all likely played at least one MMORPG. Be it World of Warcraft, Final Fantasy Online, or the dreaded Runescape, we all do try at least one. Aside from playing an offline RPG, whereas we have to shop in the preset stores, or loot from monsters the items we need, part of the benefit of playing an RPG is that you can gather the items, equipment, and materials for the game from the other players.
There are several different ways this is done, through the means of Auction Houses, Player Vendors, and Player-to-Player trading.
I've seen 2 styles of Auction House. The first allow players to post the items they have for sale at a price, and the players bid on the item until the time runs out, slowly raising the price. The second version allowed the seller to set the price, and allow the player to bid randomly, giving the player the item only if they bid higher than the sale price.
I've also seen 2 styles of player vendors. The first being that the seller could set the items for sale, and other players could just click them to browse their shop as they were passing by. Allowing the player to fully move around with the items for sale as a travelling merchant. The second style restricted players to certain areas of town where they are forced to stay until they stop selling. Sometimes taxing the player or seller for the items depending on the sale area.
Finally, we come to the method of player to player trading. This final method involves the players seeking items to ask around when they are looking for certain items, then to barter with another player who is selling it until they come to an agreement, and a trade takes place.
I'm fairly certain there are other ways for the economy to work, and if you can think of any I'd gladly like to hear them. If you have any reasons why one of these methods are better than the other, I'd gladly like to hear that too.
Without a good economy, you get unhappy players. Unhappy players won't play the game, so remember... You don't have to give players stuff to keep them playing your game, you just have to give them a good system to play it with.