Bunny Trail Alert!
That triggered a memory of flying in the 1980s, when airlines didn't handle money at the gate. Those were the days of printed tickets, and a printed ticket was the equivalent of money. So all of the airlines except Southwest would accept a ticket issued by one of other companies.
I was doing a lot of travel between the SF Bay Area and Los Angeles, mostly flying PSA and AirCal, who were head-to-head competitors on those routes. I learned that if I arrived at the gate with a reservation for the flight, with ticket in hand for travel for any Bay Area airport SFO, OAK, San Jose) to/from any LA airport (LAX, Ontario, Burbank, Long Beach, Santa Ana) I could get on the flight, regardless of whether there was any difference in fare.
I soon learned that I should simply book the cheapest fare available. Then, when I was in LA, I would call reservations to change to the flight I really wanted. They would make the change, and inform me that when I got to the airport I would be charged the fare difference. The trick was to not check bags, because if I checked a bag, they would charge the fare difference when I checked in and print a new ticket. But if I showed up at the gate with my old ticket in hand, they would take the ticket and let me.
I did that for about six years. Then one day I showed up at AirCal, and the gate agent looked at my ticket and said there was a fare difference. Since they didn't handle money at the gate, I had to return to checkin and have them print me a new ticket.
It was good while it lasted.
I occasionally flew Southwest. I got upset with them one time when I was flying from LAX to OAK after a meeting. I had one of their cheapest airfares, no changes allowed. My meeting finished early and I got to the gate while they were boarding the plane before mine. I asked to get a boarding pass for that flight, and they refused to give it to me, even though seats were available. I was stunned!! I said you are boarding a plane right now to Oakland that has seats available. "That's right." And I have a valid Southwest ticket for travel from LAX to OAK. "Yes, you do." But even though you have space on the plane and you are still boarding the plane, you won't give me one of those seats? "Correct." Well then, why don't you put me on standby for that flight? "Can't do that."
That experience soured me on Southwest for a long time. It seemed to me that if they were as customer driven as they claimed to be, they would have put me on that plane. Yes, it was a no changes ticket, but at that point, when they have a plane that is leaving that has empty seats, and a passenger with a valid ticket for the next flight between those destinations, there's no harm in letting me on the plane.