Budget airlines like Ryanair and Spirit have made flying affordable for millions, but their business model depends on squeezing every penny out of passengers. I flew Spirit to Florida for $45, then paid $30 for a carry-on that didn't fit the 'personal item' sizer – still cheaper than the train, but barely. Is the hidden fee structure a necessary evil for low fares, or just a deceptive way to advertise prices that don't exist?