In this installment of MMOconomics, we'll discuss how artificial resource maintenance can stabilize MMO economy.
To decrease flowing currency (currency is a resource too), developers add items that are purchased from NPC's. Giving the NPC's money decreases the amount in the player base and effectively removes it from circulation (Eve: Skill books, WoW: Mounts, ect.). In Eve, items are bought by NPC's as well to maintain their worth. Other methods similar to this are repair costs.
In order to decrease resources from being constantly fluxing in, games limit the amount of resources are obtainable at a given time. Although this does not make resources infinite, it does make only a finite available for a given period of time. This artificial limit decreases overall influx of resources making the supply stable.
PvP is another excellent way to remove resources from the market. If a player's ship is destroyed, the ship and all unlootable items are removed from the market. This also forces combat players to constantly input more into the market then just getting upgrades.
2 years ago