Passengers booked on Independence Air flights learned quickly that US law forces carriers to take these customers on their flights for $50 on a standby basis. Never wanting to pass up an opportunity to wrestle every dollar from people, some legacy carriers have been offering to sell people confirmed seats for $100.
Southwest Airlines, on the other hand, has taken exactly the opposite tactic (as they so often do). They are taking Independence Air passengers for free. This is why customers love Southwest.