The price of a painting or other artwork is set by the seller, whether an individual, gallery, auction house or other organization. There are up to three steps to determining a painting's value: valuation, appraisal and authentication.
Valuation and appraisal services consult recent auction catalogs and other databases to determine a painting's value. The most basic step, valuation, considers details such as the artist, size, condition and date of the artwork. Appraisal is a more in-depth study including the art's provenance and is usually done if the art is to be insured or donated. Authentication is only needed if there is doubt about the provenance of a piece of great value.