Depends on how far ahead of time you purchase your tickets. Cheapest fares on Southwest are relatively inflexible - no refund or cancellation (but you can apply the price of the ticket to purchase another one within one year of original purchase). If you elect to standby for the next flight or miss it, you hafta upgrade to full unrestricted fare.
The prices SWA quoted are about right. Ticket prices on Southwest don't rise much more above that.
I recommend you also download Southwest's DING! program... it will alert you of cheap fares in your area:
More About DING!