That wouldn't work if you had to sit there all day charging people, the opportunity cost makes that a rather bad way to make money. Now if every time somebody wanted to play they had to put a bill into some sort of mechanism incorporated into the table that released the ball needed to play, maybe that would work. But then again, people could just use another spherical object and bypass that.
Tbh not a very good idea, be it foosball or vending machines. Making money is harder than that, there's all sorts of minor obstacles that make such ideas impractical and not all that profitable. Like, where would you set it up? Populated establishments won't let you do it, or they'd charge enormous amounts for that privilege. Shitholes would charge you too, cutting into the profit, and shitholes will have less customers and shadier customers, which will probably steal your table or damage it just cause.
