The big thing in real life that sucks the life out of our wallets is our wif-- I mean, taxes and upkeep on our wealth. So, in the topic of taxes, there's plenty of them, in a civilized society the more money you got the more taxes you pay (not always the case in the US). Everything that can be taxed could probably be taxed. This would give a steady supply of money to the government which can then be used to create various roleplay situations or increase/decrease funding for government factions.
Another big thing is upkeep on the things you have. One thing RP servers always avoid is making upkeep on the properties and vehicles you own. Let's say I crash my Bentley Bentyaga into a 2005 Ford Mondeo. I'll be paying /way/ more in repairs than the driver of the Mondeo. Repair prices should depend on the car's price. Properties? Well, they have their own dynamic too, you have to pay regular bills such as water/gas/electricity, but there's always the case of something breaking or leaking.
If we increase upkeep on things and force rich players have to dish out more money this can all be pretty balanced. There's some other ways to draw money out of the economy too:
• Every time an illegal faction orders a shipment they pay money out.
• Every time someone dies they should lose all money on hand (maybe leave like $200 max)
• There should be NO way to gain money or have a financial edge over other players by donating. (Creates money that's not deserved/earnt)
• Cars should have a thing where they need to be repaired more often the more they're used. So, a used Ford Mondeo may be cheaper, but will require higher upkeep than a brand new one from the dealership. This would take cars out of circulation eventually and force people invest more money into cars.
And many more, I'm not an economist so talk to them.