-They generally have a higher capital investment costs. Most high tech devices cannot be prototyped by a guy in his spare time, unlike a web app.<p>-Difficult to scale from prototype to production<p>-Most high tech manufacturing happens in Asia, which makes it difficult for US based startups to find and communicate with reliable partners<p>-High capital investment costs mean that it is difficult to decrease the per unit cost to the point where high margins can be reaped<p>These are just a few of the considerations, and aren't applicable in every situation.