When artists agree to be represented by a gallery, they usually work out with the gallery owner such matters as the amount of the dealer’s commission; how often their work will be exhibited in solo or group shows; the price of their artworks; that sort of thing. Another expectation, usually not as explicitly stated but increasingly crucial, is that the dealer will attempt to control the market for the artist’s work even after it has been sold. Some dealers go so far as to bid up, and even buy, pieces when artworks are consigned to auction. The practice is legal.