It's also a trade in (often) one-off pieces. It's their job and skill. The gallery is in business because the staff has a feel for how much money they can get f

It's also a trade in (often) one-off pieces. It's their job and skill. The gallery is in business because the staff has a feel for how much money they can get from whom for these pieces. They do have a network of potential buyers (who are or are not currently interested in your one or two pieces). They also know the people at other galleries, who have still more contacts. These contacts are not just collectors - they are all the consultants and curators who work for them. Some pieces are bought by the gallery because it "specializes" in that artist or genre. They know what they paid and got for other pieces. Perhaps nobody else does. And then a piece is sometimes sold not just "because it's the price" but because it has sat long enough and it's time to go.