There's a difference between art and expression. Cave paintings, mandalas, sketches on a napkin, graffiti, etc. those are all forms of human expression. "Art" is something people pay for in the 21st century, "art" is a commodity. What is "art" is decided by a group of people, usually those who stand to benefit from the charade. That is why there are stories of people examining fallen objects in art galleries, as if they were a piece, just because people saw it in an art gallery. Is a urinal art or a thing we piss on? Who the fuck knows, no one will ever know, just fucking give in and go with it. Art, art, art, everyone is a fucking artist. People want to be "artists", people call themselves "artists", what the fuck is an artist? Purely a worker who makes the "art" commodity, but justifies it with bullshit and charges for it. The poor sod making alternators in a factory can't sell you it as a modernist piece that is sure to bring your art deco living room together and impress all your turtle neck friends over a glass of Tesco chardonnay.
Fuck art and fuck artists. As I said, self-expression is proletarian. Go paint some anti-government slogans in red paint on the side of a building, and you will have created more "art" than 99% of the shit made in studios.
Why do you think Banksy's "art" sells so much? Because the people behind the Banksy project were smart and they packaged their "art" as genuine self-expression, they didn't abandon the gallery, they declared the outside to be the gallery, and the bullshit they sell you is "authenticity". Banksy has several movies and a hotel in Israel, they're porky as fuck but they are great at making a show and making you believe it is not "art".