>Empty speculation without evidence

>economic losses imposed by hours-long closures of major arteries

Your are correct, that is what you did there. The vast majority of economic activity in urban areas comes from local people walking, biking, and taking transit. Very few people in cars are actually stopping and spending money in the city. The only people in that group negatively effected by this are bus riders, which should be considered.

Businesses complain when cities want to remove street parking or pedestrianize the street they're on because they've been told that it will negatively effect their business and reduce the number of customers they get. The reality is the opposite. Removing cars from an area almost always increases economic activity for businesses. If you walk around coffee shops, retail, and restaurants downtown during events like this, it's pretty clear evidence that holds true.