When I was a student in Chicago, I didn't take my car, and I generally flew back as Amtrak is garbage and the bus is hit or miss. I was there from 2009-2011, United did special Friday night departure Sunday return deals, generally sometime early in the week, starting Maybe Monday and ending Thursday morning, United deeply discounted most of their Friday evening flights from ORD that were geared more towards regional business destinations, and they required a Saturday night stay. AA and Delta would often follow suit, picked up a few tickets for $60 or so. Otherwise, at that time the standard fair was usually about $450.

I will be taking the Chi-CVG-Chi route again as apart of winter travels in January, and the Southwest effect is real, picked up a one way on AA from ORD to CVG for like $40 and I picked up a return to Chicago on WN for like $50.