Ownership costs are so low because utilisation has been improved greatly over the past decades. Especially short-haul planes are now in the air for 14-16h or more. That over a life-time of two decades or more reduces the per-flight cost to a minimum.

Meh. To that same point though, Boeing's net profit margin is only around 10%. Of course, 10% is pretty typical of any company, and doesn't seem to be any kind of huge amount coming from duopoly power. Compare to Visa, which has more like a 50% profit margin.

...But even if you considered all of that 10% profit margin comes from the powers the duopoloy affords them, then that's only 2% of airline costs (10% Boeing profit * 20% of airline cost).