Apparently there will be both consumer and enterprise pricing, whatever that means. I'm guessing $500 to start at consumer level with lower resolution, less battery life, etc. Twice that for Holo Pro.
Sound is easy enough - a pair of decent headphones can produce fairly decent 3D sound, and combined with the illusion of depth provided to your visual system, I suspect it will be extremely convincing.
I'd assume for sound that it doesn't use headphones so much as bone conduction so that it doesn't get in the way of natural sounds. From the design, it seems that there's some kind of device-skull contact most of the way around.
Sound is easy enough - a pair of decent headphones can produce fairly decent 3D sound, and combined with the illusion of depth provided to your visual system, I suspect it will be extremely convincing.