Southwest flight prices do actually change frequently. There are several types of fares to choose from and the right one can get you a refund if you spot a rate change at some point. If you select the anytime or business select fares and the rate goes down, you can get a refund for the difference in prices. If you choose a different fare type you may be entitled to credit only. There are exceptions to these guidelines which you can find in the faqs as well as in the complete set of terms and conditions on the Southwest Airlines website.