What will it cost?
It's a new technology, and cost will depend on wide adoption, mass production, and competition.
At first I expect it will be cost-prohibitive for all but the high-end. But it will plummet if it works and is adopted.
Consider: In the mid 1990's, flash memory was typically $200 for 1MB, and only crazy rich people used it. Today it's around $20 for 16GB, and everybody has a couple "thumb drives" laying around.
That's a cost reduction of more than 150,000:1 in only 15 years! Heck, even 10 years ago, no one in their right mind would have predicted that Flash would become so inexpensive. It's all about competition and mass production, once something is widely adopted.
The "early adopters" always pay a high premium.
More than 4 cars but just one will work great in a flashlight! ;-)