What is the concept of art value?

What is the concept of art value?
Art value has a lot of dimensions.
1.Historical: The significance and contribution to a specific genre by an artist.
2. Masterpiece: If the work is by a well known artist, such as Picasso, or Warhol the price will be greater more so it it is the last painting of its kind than that of an unknown/ new upcoming artist.
3. Antiquity:It also depends on the antiquity. Some older paintings, although done by lesser known artists, still hold art value because of how old they are. Particular works that played an essential role in certain art movements also have a lot of art value. For example, Braque represents cubism.
4:Popularity: Added concepts include what art is popular to the masses and critics, and what sells.
5. Quality,uniqueness and medium used in the art work.