The USA has a Wal-Mart mentality. WN is simply the Wal-Mart of the airline industry. US Airways is more like Belks.
I have started moving my business around in the town where I live. When I have people tell me that they flew on so and so because its cheaper, I do the same thing. I tell them I bought my groceries, for example, at Wal-Mart instead of their store because its cheaper (although I hate the service ,or lack thereof, at Wal-Mart). But when I buy clothes I go to Belks because the quality and service is better.
Where you got your analogy wrong is not only is WN cheaper, ie Walmart, it provides better service in coach the US ie Belks. 737, free drinks, overhead space, friendly employees, higher frequency, more room, faster award ticket........