> the Vimes Theory of boots (rich people buy boots that last generations, poor people buy boots every year)

This made me think of a fascinating exception to this

Luxury-brand cars usually get turned over every couple years so as to avoid their inevitable maintenance cliff

It is an interesting exception.

The really rich people that I know of drive 10-year-old beaten-up Land Rovers, though.

I think there's a nouveau-riche slice of folks who buy "luxury" cars thinking that they confer status. There are brands like this in every industry, that adopt all the pointers of "luxury" except actual quality.