No one knows for sure, except Sony, how much the A7s will cost; it's all but a guessing game by everyone else. Some say it would cost $2500, others say it would be the same price as the A7. Personally, I want it to be priced around the A7, or very slightly above it. No doubt the A7s is a very interesting camera with phenomenon low light capabilities. For all intents and purposes, one may never need to carry, and use a flash again on this camera; it could literally see in the dark. This is its strength, as depicted by the S in the model name. Less so, is the 4K capability. The dependency of an outboard 4K recorder will limit the use of the camera in certain circumstances, and it will add bulk to the system. Video-wise, it certainly is not as indie friendly as the Panasonic GH4, which has internal 4K recording capability.
I think most people will buy this camera for its still picture capabilities. The already mentioned low light capability, the very high dynamic range, the compact size, and finally the small file (depending on your usage, of course), all together makes a perfect carry around camera. This is why I am so interested in it. I believe it would be wrong for Sony to price it at more than $2000, since it does not cost them any more to make than the A7; the only difference is the sensor, which I think should have better yield than the higher density 24MP sensor used in the A7, thus lower in cost.
I look forward to a reasonably priced low density full frame camera, as would many people who are interested in image quality and megapixels. Once people find out how good it is, they will not go back, barring any earth shattering sensor designs that trumps the A7s.
Desk & Chairs - Canon 5D Mark II & Schneider-Kreuznach Componon 80mm f5.6 Enlarging Lens.