Airlines are increasingly selling their lowest fares on their own Web sites. Consumers who rely soley on third party meta search or online travel agencies will often end up paying more than they should. Spirit Airlines is just one of a score of carriers that are attempting this strategy.
When researching this route between Chicago and Myrtle Beach, Airfarewatchdog.com fare analysts compared both sources (Kayak.com and Spiritair.com) and found a lower fare on Spirit. They then listed the lower fare, sending users directly to Spirit's site, even though Spirit does not generate any revenue for Airfarewatchdog.
Same flights, routes and dates, but very different prices depending on where you buy: