Ask HN: What is the field of economics studying “arbitrary” value?

A shirt is made somewhere in an given factory.

The shirt was made from raw materials, energy, labor. Maybe, some part of the labor was marketing - a couple people worked on an ad in the local news, a model was paid to showcase it on the website and maybe in an online ad.

I can imagine how the various money transactions associated to all those activities are tallied. The various elements in the value chain adjust their prices to make a living margin, this drives the final "retail" price, the government collect taxes, etc...

Now, for some reason, the shirt is picked by a modestly famous internet celebrity. Suddenly, copies of the shirt are sought out everywhere, and some seller is incentivized to bring the _retail price_ up. More money exchange hands. More taxes are levied.

Naively, it seems like this "value" was created out of "thin air (the shirt is not any warmer or resistant or durable or anything tangible).

Is there a name for this kind of "value" ? Afield of economics studying it ? Some relatively serious book or author on the subject ?

(My overal question what "how much of a western country's GDP is made up of 'we bought this because we needed it' vs 'we bought this because it's cool, like', so even "pop"-science would be interesting.)