Sub 100 is definitely possible. Just consider the $100 laptop project. They estimate the current price at $150, but expect to bring it down to $100 once mass production starts. And that includes screen and battery, which is not required for a neo-micro. It may be production cost rather than retail price, though.
I read a bit about the $100 laptop specifications today and was a bit disappointed that it uses an x86 CPU from AMD. An ARM would seem more appropriate (lower cost, lower power, integrated LCD controller), but I guess the designers took the path of least resistance with x86 Linux.