Value disappears when appearance becomes the only feature being purchased.

When appearance is the only thing being bought, the value evaporates as soon as anyone stops looking, including you. Things bought to be seen have a short satisfying period and a long ownership period, and the second is where most of your life with them happens. Nothing remains once the novelty of being seen with it wears off.

Before buying something you find impressive, imagine owning it with no one aware of it. If it still appeals, that is a genuine preference.