When it comes to art its rarely (if ever) about worth and all about the fact that its a "one off"

If its a production item like a car or watch, I've found its usually about bragging rights.

Its hard for someone that does not have a billion dollars to understand how you can spend $120 million on a painting, but then again a third world family in poverty can't comprehend that we would spend $100 on a razor.

Economies of scale.

To answer your question, yes, I believe that a thing is "worth" whatever someone is willing to pay at the moment. Not sure if you're the appropriate age but do you recall people paying $10 for a pebble because someone called it a pet rock?