The fares on Southwest aren't really low any more. At least, comparing them with United for flights out of Chicago, I don't find any real difference in prices,

The fares on Southwest aren't really low any more. At least, comparing them with United for flights out of Chicago, I don't find any real difference in prices, even on regular Economy fare. The only advantage that Southwest has at this point (and it's a very important one in some contexts) is that it doesn't have any change fees.