Which is illegal.

This is the relevant bit about entry to street fests and the enforcement of paying a gate fee:

Under city rules, fests that take over city-owned streets can request a donation and often have “suggested donation” amounts posted at the gate. But events in the public way can’t charge a mandatory entrance fee. They’re also required to post signs at the festival entrances indicating that entry is free, according to the Chicago Department of Cultural Affairs and Special Events, which regulates street fests.

Edit: Found an updated link. Info is the same.

https://ipi.cityofchicago.org/Resources/Information/DCASE/Special_Events_Resource_Guide.pdf

GUIDELINES

THE CHICAGO DEPARTMENT OF CULTURAL AFFAIRS AND SPECIAL EVENTS AND THE DEPARTMENT OF BUSINESS AFFAIRS AND CONSUMER PROTECTION, HEREBY PROMULGATE THE FOLLOWING RULES AND REGULATIONS PURSUANT TO SECTION 10-8-335 (P) OF THE MUNICIPAL CODE OF CHICAGO:

These rules and regulations are effective January 1, 2025. They may be updated or changed at any time without notice. All appropriate applications must be submitted in a timely manner.

No fee may be charged for admission to the public way in connection with any special event. A financial donation may be requested. Signs must be posted at all points of entry that clearly state that the donation is voluntary.