How much would it cost to make one?
So let's call it $50k, built and ready to use =)
those cameras are $1.5k each...17 of them.
Edit: Actually, those lenses are around $700/each as well. And you would definitely want a professional putting it together for you with that kind of money. So $100k probably. Definitely made for industry/production use, not for someone trying to film a weekend trip in the mountains haha.
Non-direct source has price listing http://www.edmundoptics.com/cameras/usb-cameras/point-grey-g...
The GoPro Omni and the NCTECH IRIS360 may be a little bit closer to the indie scene rather than the professional scene, but those solutions are still $2000 - $5000... and are only 4-6 camera solutions.
[1] http://www.360heros.com/2014/01/worlds-first-fully-spherical...