This seems like a bad idea for Southwest.

Just about every time I go from Google Flights to SWA, "hey I wonder what the SWA flight costs," I am shocked that the $250 flights on Google Flights are $450 on SW. This seems to happen for any flight of more than a tiny hop distance. I don't book 364 days in advance so I can't speak to how their fares go up over time.

It always seemed to me SWA had a bit of a moat with their customers. They just go straight to SW and book, knowing there are no extra fees and free bags. And probably thinking its the cheapest as there is no easy way to compare. And never checking elsewhere. "I fly Southwest!" Now that will be exposed to some degree.

As an example, that I would call typical, I see SAN-CMH at around $300 RT (or $250 if you want Spirit!) in June. Same fare is $470 on SWA.