Harry Potter artwork on sale

This story from Ananova reports that the original artwork from the first Harry Potter book, Harry Potter and the Philosopher\’s Stone, is to be auctioned at Sotheby\’s of London and is expected to fetch about 25,000 pounds sterling (just under $40,000). It is a 1977 watercolor by Thomas Taylor, though the editions I have seen of Harry Potter and the Sorceror\’s Stone (as it was called in the US) had a different cover, I think.
Sotheby\’s will also be auctioning a letter in which JRR Tolkien apparently accuses Walt Disney of being a business cheat.