Can someone please explain to me why the 12-24 lens would be, on average, $300 more. It seems to me that the 10-24 would be more since you get an extra 2mm and the availability to go to f10 with it. Both are G ED-IF AF-S DX type lenses. I am on the fence between the two and am leaning heavily towards the 10-24 since I have heard great things about both of them. Also, didn't the 10-24 use to be $799? Thanks for any input you may have!