Quite a good look inside canon's factory if you can stand the announcers voice 
It's easy to see why these big lenses cost so much now with the amount of time and effort gone into making them.
[http://www.canon.com/camera-museum/tech/l_plant/main.html]

It's easy to see why these big lenses cost so much now with the amount of time and effort gone into making them.
[http://www.canon.com/camera-museum/tech/l_plant/main.html]