The price of the paintings are decided based on the artists’ value in the market. Art lovers look for quality signals before buying modern art paintings online or from an art gallery. Those signals can include curators’ review about artists, if their artwork was exhibited in art galleries or museums, or if influential collectors have shown interest or bought their art.
Some artworks cost more because there is consensus in the art world that those works should be sold expensively. Art caters to the market of unique objects, so it satisfies the scarcity among art enthusiasts.