That is only true for property tax which is slightly lower in the city than the suburbs. If you include Sales tax Chicago is higher.

Property taxes are fairly variable in the Chicagoland area, but there are many places where Chicago is not slightly less, it’s dramatically less.

The sales tax is floored by the state sales tax which makes up more than half of the total.

The Cook County minimum sales tax is 8% with lots of localities matching Chicago’s 11%.

All told I imagine tax rate in the Chicagoland area largely depends on a whole equation of property value/tax & consumption. But I’d be shocked if Chicago was universally more expensive than its suburbs.

Chicago's share of the sales tax is 1.25 percent. It's really not any higher than anywhere else in Chicagoland.