I saved at least $150 over what other airlines were charging at the late date I picked my flight, and if I wanted to maximize my savings, I could have packed all my clothing into one carry-on, ordered no food on the plane, and sat wherever they wanted me to sit.But here's the thing: I actually much preferred paying for food instead of getting it for free. Why? Selection. Instead of getting a bag of nuts and half a can of Sprite Zero, they had a menu with various low-end snacks. They were as expected, a complete ripoff -- but not to the point of being highway robbery. And certainly not expensive enough to eat up a significant chunk of the savings vs. flying on a conventional airline.
The New York Times describes the CEO's explanation of the business model this way: "Mr. Baldanza points out that if you don't check any bags and don't mind taking whatever seat the airline gives you, you won't spend an extra dime. To him, it's all about unbundling. Why should a person who isn't checking a bag subsidize all those bag checkers, for whom an expensive infrastructure is bought and maintained?"
He's 100% right: Spirit Airlines' model is just better for everyone and its more bureaucratic competitors will catch onto that soon. There is a certain percentage of travelers who really just want to get from point A to point B as cheaply as possible, and "niceties" like in-flight movie and food can be done away with in exchange for cheap fares. Court these people, make sure they know what to expect (nothing), and you just might have a model of growth for the future.