cheaper lens????
Sony lens are generally abit cheaper than similar lens from Canon, with only the 50mm f1.8 as an exception. But its only 1 lens that Sony sells more expensive, the rest Sony generally sells cheaper.
Not forgetting Sony Alphas can use Minolta lens, which is even cheaper~
And when u compare 3rd party lenses, then u will realised the difference.
Tamron 17-50mm f2.8 with image stabalization for Canon and Nikon cost $950.
Tamron 17-50mm f2.8 for Sony mount is $630, and it has stabalization too due to Sony Alpha.
So just a simple lens comparison, and u will realise that Sony lens and 3rd party lens will be cheaper than Canon and Nikon.