It could very well be a EOS Movie prototype. I'm sure they are out there.
As to pricing of the 5D MK III, Nikon Rumors has a price estimate of $3K for the D800, which is where the D700 started. I doubt that a 5D MK III will be far off this price.
Yep. If you look back over the previous 17 (!) pages, you'll see that several people have 'discovered' that there are two different cameras pictured (seemingly the 1D X and this new prototype).
Very nice detective work indeed over the last 19 page of post here! I too like the idea this could be the EOS movie camera with the form of the LCD display. Could this mean they might announced it before a 5D mkIII though?