Earlier quoted context omitted.
I’m not sure that’s anything other than math. If I have a property and I decide to rent it, why would I rent it for anything less than the sum of my expenses plus a profit margin that will cover maintenance or repairs? Why would anyone else? A rental property is just like any other business.
Should an airline let a seat fly empty, or accept a price that’s less than the cost plus profit of the seat?
Note however that airline pricing is notoriously difficult. There is no single price at which an airline may be flown profitably. It is an astounding achievement that the industry functions at all.