Nearly every major study I've seen going back decades has Chicago having lower comp numbers for tech than SV. But usually its on the order of 3-10%. How that compares in cost of living adjusted terms I don't know.

The 60-90k number sounds absurd to me. Having worked in Chicago for quite some time, 60k is what a new graduate could have earned 10 or 12 years ago in the middle of the last bubble burst. 90k seems like a plausible starting point now for an entry level Java developer.

The last time I worked in a .NET shop, we would not have been able to hire any of our targeted developers for anywhere near those numbers and that was 5 or so years ago.