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.
Not saying it's a bad to spend money on temporary comfort, but it's the opposite of the Vimes boot problem.
How much money would you pay for two extra days of life? In the end, time itself is also “fleeting”, if you want to put it that way. But I sure as heck would fork over the money if I had it.
It's true that comfort isn't a permanent good you own a la Vimes. But better comfort is a decidedly different outcome and you argued that it wasn't.
A hand-stitched leather suitcase is expensive. It will also last until your grandchildren are dead.
The grandkids not wanting it may still apply if they are still minors, there would be plenty of time for tastes to shift again.