You're looking at the Limited Edition Mystery Masterpiece pen, the result of a collaboration between Montblanc and Van Cleef & Arpels. To celebrate their centennials in 2006, the two companies made a total of nine pens, each with 840 diamonds and over 20 carats of gemstones. The pen is valued at $730,000, making it the world's most expensive writing instrument.
Link - Thanks Sinthyia!
World's most expensive crap! We coated it with diamonds. Stupid. Everyone should ignore this junk.