It's all about scale

By scaling transistor dimensions down into the nanometer realm and scaling manufacturing capabilities up to produce billions of individual chips, the semiconductor industry has achieved economies of scale over the past 40 years that allow what was once mainframe capability to be affordable to everyone in the world in something as small as a cell phone. With many fundamental physical scaling limits still far away, this progress can and will continue if demand for the applications supports the increased investment necessary to get there.