The term "art market" is used to refer to the trade in works of art. Artists sell their creations through intermediaries (galleries, auctions) or directly to art lovers. These transactions are not regulated.
The artist is free to set the price according, as in all commerce, to the law of supply and demand.
The rating, an economic consideration, does not represent the value of the work which is subjective. The two are, however, often linked. So that the potential buyer can find their way around, the works of artists who have already been the subject of transactions are listed with a notification of their price. However, only auction results are recorded. The amounts of sales to galleries or to the artist are not cataloged. For each sale, a certificate of authenticity is issued, but the sale price and the name of the purchaser are not included.
Depending on whether it is modern (ancient) or contemporary art, that is, created by artists who are still living or not, the procedure for establishing the rating of an artwork of modern art is different.
The experts of each artist rely on the results of the auctions.
They know exactly the market price and are able to properly estimate the work. Their expertise is based on the artist's existing work since his production, in the case of old art, is not renewed. Prices vary depending on the economy and popularity of the artist.
A retrospective of an artist in a large museum helps raise estimates for upcoming sales. In the case of a buy for an investment, there is no fair price, the odds are fluctuating and unpredictable.