This is an opinion piece wrapped around exactly one piece of data, which was an "extrapolation". This blog or opinion column is really NOT news at all.
While marginal costs are important in revenue management in the airline industry, they also have tremendous overhead and infrastructure costs that they also must pay. Frankly, if you've noticed, the airlines have recently been profitable ONLY becasue of the fees. The fares simply don't cover the total cost of running the airline, even with the tremendous technology-based efficiencies that airlines have taken advantage of over the past quarter century (e.g online reservations, online check-in, check-in kiosks at the airport, etc. have cut down tremendously on the number of airport employees required).