Electronic resources relating to book sales are available via OxLIP+. These include American Book Prices Current, of use to anyone tracing the books through recent auction sales, and the Jahrbuch der Auktionspreise für Bücher, Handschriften und Autographen, available from 1950 up to the present.
Many of the major auctioneers allow you to search their webpages for recent sale items:
Still looking? Below is the spreadsheet of raw data regarding Sotheby's and Christie's catalogues. This was created for librarians but it might be useful as a last resort!