Right, but big plants don’t drive CoL increases because they are built far outside the city, and the people that work there typically live/build houses in more suburban/rural outlying areas where there aren’t many constraints on land availability (so people moving there do not really increase the prices).

The Gulf Coast has hundreds of large manufacturing facilities that employ millions of people, and is one of the fastest-growing areas of the country in terms of population. Yet Gulf Coast cities have some of the lowest CoL in the country.