If the market value is what people are willing to pay, then you've just ignored any responsibility for answering the question "what are people willing to pay for", which is exactly what the question "where is the value" is supposed to be answered by.
In other words, you've just swept a messy question under a rug and acted like we'd all be smarter if we just called the mess "a rug" and ignored the details. Economists talk like that because they don't care about the art (they care about economic abstractions.) But you can't think like that if you want to answer questions about art, because those abstractions break down if you do.
Anyway, I think all damages should be capped at the original price point, 100$, even in the absurd case the judge sides with the buyer.