From that report:
In the last five years alone, between O’Hare and Midway airports, the FAA reports nearly 1,500 bird strikes.
Would a price tag of a billion dollars on that be reasonable? That's assuming they all landed safely, too. Cost of loss of flight, plus aircraft out of service while the engine is fixed, plus cost of fixing/replacing the engine must add up to a fair bit. It's almost one incident a day.