Put another way, 70k in Alabama is probably more like 110k in Chicago. You could pretty easily pull a 350k house on that salary, which gets you a nice 3-bedroom in a quiet neighborhood (according to a quick search). And now a new car is now 27% of your yearly salary, rather than 43% so you can upgrade almost twice as often (or buy more books, go on more vacations, or just save more).
That's not to mention all the cultural opportunities you give up living in Alabama instead of Chicago. I'm sure Alabama has some nice countryside, and I know it's not all Deliverance-style back-country. But it can't compete with Chicago in terms of world-class theater, museums, symphony, cinema, or restaurants either.