All those cheap copies of the Mona Lisa don't seem to have harmed the popularity or diminished the value of the original. People still queue up with their phone-cameras to make cheap copies for themselves. It doesn't seem to have affected its "uniqueness" either.

That's more of an issue when dealing with art objects that have been digitally mastered. In that case, there's no "original"; each copy is, potentially at least, as good as another. Art galleries are still trying to come to grips with that problem, which undercuts the mystique they've been trading on all these years.