In support of the argument that the ~$1400 price is merely an RRP, place holder, etc, and that the final price will be something far closer to that of the 35mm 1.4, I think we can learn something from the specs.
One point made was that the 50mm might be more expensive than the 35mm due to the fact that the design requires more glass. I don't think this is true because of one thing: the weight. While both lenses share a very similar outward design, the 50mm is slightly bigger. BUT, while the 35mm weighs 665g, the 50mm weighs only 470g (
http://www.dpreview.com/products/sigma/lenses/sigma_35_1p4 and
http://www.dpreview.com/products/sigma/lenses/sigma_50_1p4_a respectively). There is obviously less glass in the 50mm.
My theory is that the design is less sophisticated and so there is a very small likelihood that the price would be more than the 35mm. I might be totally wrong but I thought I'd share this