Leave it to Leica to produce the worlds most expensive lens. Sheikh Saud Bin Mohammed Al-Thani of Qatar had this lens specially designed and shipped to him for a cool $2,064,500. This 1600mm 5.6 lens is the biggest and heaviest Leica has ever made and although it is a one of a kind product, you can see the prototype of this lens (the one in the picture above) in Leica's factory showroom in Solms, Germany.
Obviously stabilizing a lens of this size is a feat in itself and it has been reported that the Sheikh who bought it also commissioned a specially designed Mercedes to carry and steady it. Sadly the Sheik has never released any of his images taken with this lens so we will never know how it actually performs. I hope I'm around in 50 years when this thing shows up on eBay.