One of the reasons cited for cancelling the main fireworks show is the cost of policing it. Here is an excerpt from the article that describes how this went last year:
To be sure, that's a hefty sum to spend on policing a fireworks celebration, but the number quoted in the article is not the actual economic cost of policing the fireworks. To know the economic cost, we need to know the cost of the alternative. In other words, we need to know how much we would save on policing by slashing the main fireworks show (or even if we collectively save anything, given that MPEA is putting on a replacement show at Navy Pier).
Instead of having one fireworks show on July 3 that drew more than 1.2 million people and stretched city services to the brink, Chicago held smaller synchronized fireworks shows on July 4: at Montrose Harbor and 59th Street to coincide with the previously scheduled show at Navy Pier.
City Hall hoped to cut security costs by making the switch, but it didn’t quite work out that way.
Policing three fireworks venues cost $756,476, including $251,377 in “regular tour pay,” $444,251 worth of “accumulated compensatory time” and $60,846 in overtime, records show.
Maybe the savings of putting on a small fireworks show is considerable relative to putting on a large display, but the authorities won't cut extra policing to zero. In fact, I expect many Chicago police officers are working overtime tonight. With or without a large public fireworks display, they should probably be on call when a significant fraction of Chicago residents is setting off fireworks.