Hate to be negative (I think it's always great when someone can route a pinball), but there are many issues:
1. If it breaks down, it isn't earning money
2. If it breaks down, your losing money in parts
3. If people get bored, it isn't earning money
4. What does the venue want for it's cut
5. What local city taxes do you have to pay as a coin-op business
In short, it seems impossible to turn a profit on a pinball. Seems like you'd be lucky if you could earn enough money to pay off the price of the pinball.