Well... as an engineer working on a similar, but less expensive and way better looking
bike light, I can tell it is not the components that cost. Electronics add maybe 4$ to this project.
Main expenses are probably R&D and marketing. Still, 100$ implies a bit too large contribution
from the backers to get their production costs down. After that they may reduce the price,
but not holding my breath for it. Just my biased opinion.

Project I'm working on: http://vd.ee
and a brief Velodroom trailer/teaser