Conclusion
In the end, you just need to make sure that you keep things consistent. The value of your currency shouldn't increase or decrease over time. The value of items sold in stores and items sold by players might increase and decrease, but this is based entirely on the rarity of the item. You should also consider having a cap on items however, so that eventually no more are ever sold in a store. A real life example of this are things such as limited edition collectibles which only have a few thousand or hundred produced.
Players should earn less than they would in a real world job per hour of Graal work (since you're calculating in living expenses). Try to balance the jobs so that they mostly pay out the same amount per hour. This will prevent players from flocking to the "highest paying" job from the start. Of course, there is nothing wrong with having a few jobs that pay more but which require expensive tools or more work per hour. So long as the effort/expense equals the amount of money earned.
Summary
So to sum this up for people who do not have the patience to read (though if you don't have patience you shouldn't even bother managing a playerworld), here is a quick overview:
1. base your game currency on real world currency to keep things accurate and to scale
2. shops need to work on supply and demand and also strive to make profit. shops that don't make profit will not supply more items.
3. make sure that you take into account the living expenses your players would have but aren't accounted for directly in the game.
4. create plenty of ways to remove money from the economy without it entering back in.
5. keep corruption, bug abuse, and cheating in check and make sure you log anything that involves money or items, and try to limit the amount of "staff created" money or items.
I hope this article helps some managers with their playerworld projects, even if you don't use all of the steps. Good luck with your playerworld!
