The honest answer is that I don't really know but my one data point is that in 2004 Sony used it in the X505VP to create an ultra slim laptop that was really cutting edge as far as thinness and weight were concerned. Granted, the device was cripplingly expensive (starting at about $2500 I think) but how much of that was down to the carbon fibre and how much to do with the other components and Sony putting a premium price on it I don't know. I would hope that with 6 years to improve production techniques, and with the volumes that Apple would purchase (no reason not to use it on the iPhone 5 as well), that it could be affordable. It would be flat sheet rather than moulded like the Sony so that should help with costs too.