But that is all a different matter. The relevant discussion is not about trying to prevent people from spending their money for useless things. It is about the relationship between economic value and actual utility. Any transaction for a car seems to produce the same economic value, but can have vastly different social utility. Therefore, arguments that certain behaviors should be accepted because they produce economic value which must have social utility are wrong. So perhaps it does make sense to tax the rich, even though GDP or other economic value measurements will go down, because social utility will not go down proportionally.
The price you are willing to pay should be equal to your utility of the object.
But people with a lot of money tend to spend it quite "wisely" (a survivor-ship bias, since a fool and their money is soon parted).