Eh?
MTA: $104/month, unlimited
Muni: $74/month, "A" pass
CTA: $100/month, unlimited
You can buy a car for $150/month, and call it another $200 for gas/insurance, so $350 total.
The rent difference is way more than $350/month for an equal size/quality place.
Then consider all the other costs of urban living, like high sales tax:
SF: 8.5%, Auburn: 7.5%
NYC: 8.88%, Westchester: 7.38% (!)