Intel's next-gen iPhone mockup
anandtech.com
anandtech.com
So if it had a touch screen the size of a pad of paper, had an iPhone(ish) interface, had some decent productivity apps, could play music and most importantly surf the web, I'd pay $1,000 to $1,500 for it.
it would be fine if you had an 640 pixel width or higher, though I personally would rather have a physically smaller phone with high DPI.