What someone is willing to pay is not the value of something especially in a bubble....
I'm afraid you're wrong: that's exactly what the value of something is, by definition. Whether it's in a bubble or not is irrelevant (I'd happen to agree by the way that Bitcoin probably is a bubble on the principle of walking like a duck, sounding like a duck..... etc., but again, that's irrelevant).
Otherwise you're in the Lewis Carroll territory of choosing your own meaning of words: interesting concept, but hardly useful as a means of communication.
As I said, there's a big difference between saying "X has no value", which is demonstrably not true, and "I believe X to be overvalued".