The cost of living in Chicago is amazing for a Top 3 metro. My theory has always been that the winter weather discount is baked into the CoL.
1. Population decline. 2. A very large amount of good housing stock. Chicago's completely flat with solid public transit reaching out to the suburbs. 3. Lower proportion of tech and startups. Similar to how tech has driven up the CoL in many cities, the relative lack of tech in Chicago has kept CoL down.
Winter is rough in Chicago, but the CoL in Boston has skyrocketed which invalidates that as being the _only_ reason.
Your dollars go further in Tennessee, Florida, or Texas (all of which have no state income tax).