Pre-sale estimate

The fair-market price range, low and high, it is listed with an auction lot as determined usually by auction-house professionals, sometimes working with an appraiser. This estimate is often the basis for establishing the reserve price or minimum price, and is a valuable guide for prospective buyers. Sometimes the Pre-Sale Estimate is altered just before auction if the market for work by the artist has recent change. Source: www.sothebys.com