Here's what their site says ...
"Our fares are so much lower than other airlines because we keep our costs lower. For example, we book our flights only through the Internet, so there’s no expensive call center or 800 number to operate. We fly new, fuel-efficient jets so our fuel costs are lower. And we fly into smaller, regional airports where it’s less expensive (and more convenient) to land. We also allow each passenger to pick and choose the options he or she wants, making fares lower for those who don’t need the “extras”. These and other factors make it possible for us to give you great service at a price you’re sure to appreciate."
