I'm a SWA pilot and I'd agree. We are rarely the cheapest in the short term. However I don't know that you can extrapolate that to us not having the cheapest fares. That can be a function of how many seats we have remaining to sell on that particular flight.

Remember that we do allow you to board early, thereby picking any seat you want, for a small fee. ;-)

I've heard Gary Kelly talk about this very subject and he strongly believes that it's working. There is no reliable metric to measure what a customer would have decided, only what they actually did decide. So it's hard to say that charging for bags is really making money for the legacy carriers.