>Also, people live in big cities for a variety of reasons. One the biggest ones is finding better jobs. If his current job is not paying enough to live by, I think that living in Chicago offers a lot more opportunities for him to get a job that does.

That's kind of a treadmill, though. There's no real point to moving somewhere chasing a better job if any increase in salary is going to be eaten up by extra taxes and living expenses. I could get a job with a substantially higher salary if I moved to SF, but at the end of the month I'd have less money.