On the left is a piece of Leica glass that costs them $900 to produce. On the right is a piece of Nikon / Canon flourite ED glass - their good stuff - that costs about $20 to make - that's according to Leica, anyway. The Leica glass certainly looks better and it weighs a lot more.
Read the my fullhands-on Leica M9 article >>
Note: disregard the chips in the glass. These are both sample pieces of glass and have been dropped numerous times. The chips have nothing to do with the comparison.