Perhaps for the one you are with, but the Human mind has a funny subconscious that is always considering the possibility of getting something different. Monogamy does not actually seem to be a natural condition for humans.
No, the point I am making is much broader and more subtle than you seem to be taking it. Virtually everything we do socially is intended to lead back to somehow getting sex out of the deal. Our personalities, the way we dress, the way we talk, our gestures, etc.
One of the reason the aristocrats wore frilly clothes and ridiculous shoes is to send the message to everyone that "they don't work." Showing everyone that they don't work tells people immediately that they are rich, and for Males, that is a powerful aphrodisiac to attract potential Females.
Females also had methods of broadcasting beneficial characteristics about themselves.
We see the same dynamics in modern society, they just manifest in different ways, such as this current Apple Watch. The Tesla roadster is another example of such a dynamic. "Wait till the babes see me in this!" I suspect a lot of buyers think. :)
It’s not always about the cost or opulence of a product. Sometimes a product will get adopted by a group and having it becomes a kind of “secret handshake”. Subarus, Birkenstocks, and Doc Martens come to mind.