Creating resources endlessly is an issue but completely closed systems have their downfalls too. Take a look at shattered world. Completely closed economy with player run shops, banks, etc. Monsters in the world were actually equipped by items purchased from player shops by the game. The hoarding instinct mentioned above killed the game though. There were taxes but there was also a player monarch who surprisingly also enjoyed hoarding of money.

To make a closed system work you need to give the rich players incentives to spend their money. This is similar to the classic open economy with the caveat that rich players giving money to poor players helps this system while it does little for the open one. One interesting way to do this is to put in place systems to allow rich players to "hire" poorer ones out. One could require large reserves of stone to maintain their opulent castle, much more then they could mine on their own, and allow them to have an NPC reward money from their vaults to players who help supply stone for the keep.

Depending on how other resources are handled in the game you may actually end up with large amounts of deflation with infinite veins etc mentioned before.

Creating resources endlessly is an issue but completely closed systems have their downfalls too. Take a look at Shattered World. Completely closed economy with player run shops, banks, etc. Monsters in the world were actually equipped by items purchased from player shops by the game. The hoarding instinct mentioned above killed the game though. There were taxes but there was also a player monarch who surprisingly also enjoyed hoarding of money.

To make a closed system work you need to give the rich players incentives to spend their money. This is similar to the classic open economy with the caveat that rich players giving money to poor players helps this system while it does little for the open one. One interesting way to do this is to put in place systems to allow rich players to "hire" poorer ones out. One could require large reserves of stone to maintain their opulent castle, much more then they could mine on their own, and allow them to have an NPC reward money from their vaults to players who help supply stone for the keep.

Depending on how other resources are handled in the game you may actually end up with large amounts of deflation with infinite veins etc mentioned before.