Do you have any cash money (of the physical kind) near you? Are any of the bills old and worn?
Money is so interesting if you think outside the scope you personally use it for. Physical bills and coins, they all stay in the system, making the rounds as people buy and sell. How many hands have touched the same bill since its creation? What was used to pay for it? I see potential for a series of short stories that are connected through the money being spent in them, but that’s a bit too long-form for my tastes right now.
Still, money that was once stolen from a bank could very well be paying for some old lady’s breakfast, only to be used in shady dealings a month later. I say “a month”, but I have no idea how fast money gets around. I can imagine the lower-value ones move a lot more, since they’re used in giving change and everything, whereas $100 bills will generally stay in the cash register until it gets deposited.
Makes me wish that bill tracking website worked for things other than dollars, and that people actually used it. That’s some really cool data to have!