Not mentioned yet are services as money sinks. So the player uses some of the inflated money to buy a service (like health boosts and speed increases), which is essentially intangible and at the end of the service period, value disappears from the economy. This helps to counter the feeling that the player is buying something pointless (such as vanity items) or the feeling of loss they get (such as when the items that they spent lots on get destroyed during PvP).

Ideally the services provided are ones which don't make it notably easier for the player to then farm more value. Imagine a buff service that increased the speed at which players could dig for currency, resulting in them adding more currency to the economy than is taken away through the price of the service. Net result: hyperinflation as the player can use the extra currency they received to buy more / higher levels of the services, resulting in more currency, etc.