Maybe we could sum the "active money" and the rpg management sets a limit to it (low-mark and high-mark).
If the low-mark is crossed, the management throws out money equally to all citizens in a special event (like goldrush, giving shares for public shop away etc.).
If the high-mark is reached, the management decides on an event devaluating the money, like "back friday". People will equally loose gold then until the amount goes under the high-mark again.
Of course, it would be up to the RPG-Mgmt to decide when exactly to react. It need not be directly at the mark-crossing (maybe they wait a bit for the economy to settle).
Another thing for the mgmt could be to buy out shops before they become bancrupt if they are important. The mgmt could then decide to sell shares to get the money-sum down.