Meat is expensive to produce. Insect protein is cheaper and more efficient, but insect farming technology is still very basic. http://www.openbugfarm.com
That said, there'll always be a demand for a variety of protein sources. We've had access to complete plant protein for thousands of years, but we consume more meat than ever. Vegetable protein will likely always be the cheapest, and that has been the case since the dawn of agriculture.