Where does this idea that art that is not "popularly accessible" cannot be supported by the market? Such art might not be supported by the mainstream or by the

Where does this idea that art that is not "popularly accessible" cannot be supported by the market? Such art might not be supported by the mainstream or by the "lay person" as you call them, but those people do not make up the entirety of the market. For nearly all of civilized history there have been patrons of the arts. When did these people suddenly get removed from "the market"? (Also, note that if "avante garde" art was supported by the "lay people" [meaning it went mainstream], it would, by definition, cease being "avante garde")