A painting by Mark Rothko.
His works belong to the most expensive pieces of art ever created.
One of the possible answers: some artworks are supposed to be extremely, astonishingly good externalization of ideas dwelling in minds of their authors – ideas understood as different aspects of one Being. I shall call them idealetheion(s): perfect paintings, drawings, or melodies. All of them would be eternal, nonetheless each one of them would be internalized (“perceived”) just by one human being.
Some people would be especially capable of externalizing idealetheions in forms of real shapes, colors, lines, and sounds. Other persons could recognize their own idealetheions as more or less similar to those depicted by artists, therefore they might try to assess how skillfully idealetheions have been externalized.
How could one know that an idealetheion perceived by an artist would be similar to these perceived by herself/himself? It is intuitive.
Detail from the painting Girl Before a Mirror by Pablo Picasso.
Picture taken from this site.