I think you're right on the luxury brands being less durable.
To address the second airplane example, we really have to go through all that you're buying. Namely: more leg space, faster airport queue processing, more luggage, better in-flight service. Do I value these at 3x the cost? Maybe yes.
With luxury brands, it depends on what you buy. My mother-in-law still owns and uses 1970s-vintage Louis Vuitton handbags. They are built to last.
A hand-stitched leather suitcase is expensive. It will also last until your grandchildren are dead.
Both me and the richest person on the flight are going to the same destination. They're not getting there any faster or safer. Everything else is a fleeting luxury.
Not saying it's a bad to spend money on temporary comfort, but it's the opposite of the Vimes boot problem.