Originally Posted by justageek
Of course, Southwest's walk-up fares aren't exactly cheap, as evidenced by the fact that your walk-up ticket on Southwest cost you $400 more than your original ticket on American.
Walk-up tickets are always more expensive than 21-day advance purchase tickets. That should go without saying regardless of carrier. Also, I don't think $400 difference is attributable to a single walk-up ticket as the current systemwide max is $309.