i wouldn't say he was a hobbyist, but when VVG painted the paintings they were worthless, no one would give him anything for them, so by the standards set by
the OP's lecturer it is true the paintings were BAD ART. it was only time and the evolution of the modern world that changed van gogh's paintings into good art...
I think folks are approaching this in different directions, based on their definition of "value"... a word that only really has whatever meaning is given to it in context. If the OP means "monetary" value, then the statement is absolutely correct. Will a third party move in and force the buyer to pay some arbitrary sum, having decreed that somehow their subjective definition of "beauty" has been met (say, hanging elephant dung from the ceiling for a hefty subsidy)? If not, then it really is what the buyer is willing to pay, provided the seller is also willing.
Personal and emotional value is something else entirely, and not even in the same ballpark. I think there's a lot of unnecessary argument over a word that can be defined so many ways depending on context.
I have photos of my family that I value highly, but they're not "worth" any more than anyone is willing to pay.
Doesn't bother me a bit, because in the end, they belong to me.
Imagine an undiscovered work by Leonardo DaVinci. Is it not art until it's discovered, so that a monetary value can be placed on it?
Will it have no value until greedy investors can sink their talons into it?
This whole idea that a work of art has to have ANY monetary value at all to qualify as art is so ridiculous that I want to cry, or shake somebody by their foundation. It's such an ugly way to see the world.
What do you tell somebody who's been a painter for twenty years, but who doesn't have the ambition to sell his/her work? Their work isn't art because there is no price tag? Give me a break.