The value of art is only what someone is willing to pay for it. With the exception of popular artists, whose art is valuable even if it is a half erased line on a paper towel, art only matters to the people who enjoy it.
By impressing an intrinsic value to it we remove the art value and make it merely a commodity. And that is what popular artists have become, commodities. They are no longer artists and their work is no longer art.