its funny that some people seem to think that it is poor engineering on canon's part for making variable aperture lenses. its actually a really good thing. if not, there would be no zooms that are even close to affordable.
the larger the aperture, the larger the lens, the larger the price. the size is something i think plenty of people could deal with, but not the price. this is because the price jump isn't a smooth linear price curve - it's an exponential jump. neuroanatomist pointed out the 100-400 price compare to the 200-400 price ($1,600 - $11,000). unless you are a saudi prince, that's a ton of money. is $9,400 dollars worth not having to deal with variable aperture? not in my case.
think if canon didn't offer any of those variable aperture lenses - people would be screaming bloody murder about there not being any affordable lenses. look at the 5Diii price jump. half of this forum had a heart attack. all people were hootin' and hollarin' about was the fact that they wanted an affordable FF. i'm sure that when canon does release one people will complain about that not having all the features of the 5Diii or 1DX.
i think a lot of people take for granted the amount of work/cost that goes into these lenses. they look at the f number and think, "that's stupid. it should go lower. how hard can that be?!?!? 4, not 1.2 - it's just 2.8 smaller?!?!? what, it's not a constant number!?!?!? canon is stupid!!! if i ran canon every lens would be 1.2 constant, and i'd sell it for really cheap, and we'd sell so many that we would make tons of cash!!!" sorry guys. doesn't work like that. the poor man like myself applauds the variable aperture lens because it is something that i can realistically hope for.