I guess, if it performs as well as the 4,000$ Zeiss, then the price is truly remarkable...
I am, however a practical photographer. If i need a sophisticated optical equipment to tell a difference between the 4000$ lens and the 50mm f1.4, of the common variety, then I really don't see the point of getting the expensive one.

Some suggest that Zeiss may now have to rethink their pricing policy... I disagree.
People who pay $4000 for a 50mm lens dont buy it because they need it, they buy it because they can.

I am suspecting that Sigma may actually find it more difficult to find buyers.
Most of those who live off photography will still choose a 400$ canon/nikon and those who can afford a 4000$ Zeiss will never buy a Sigma.