Art can only be art if it has an expression of meaning to it, which is almost ambiguous with beauty, in some form
Recently, humans have learned that there can be a lot of expression in the menial, ordinary, or chaotic.
Where art meets commercialism is where this problem emerges, because people are putting outrageous prices on things which require little effort to make or even envision.
If modern art, say, sold for a few dollars, I doubt this would be a problem or even a moral question to anybody.
Me? I blame the art subculture. People who spend an hour every morning aligning the angle between the spikes in their hair to the golden ratio (exaggeration) know that art and expression is important, but for me, their subject matter is usually a bit too thoughtless to qualify for my time, and the time of a lot of other people, let alone their money.
Banksy, on the other hand, rocks socks