There's actually quite an open market for imitations of great art. They're not nearly as valuable as the originals, though, because painters like van Gogh created astonishing works of art and part of the value is being able to gaze upon original proof of astonishing human achievement.

I would never repaint van Gogh, because I'd rather paint my own things. On the other hand, if I were to want a Thomas Kincade painting (for some ghastly reason), I'd definitely buy the cheapest reproduction I could find, because the original painting just wasn't that valuable to begin with.