A buddy of mine worked his way through college cleaning out meth labs in homes and motels after they had (typically) blown themselves up. They are toxic nightmares. He was especially shaken when he'd find the family photos indicating that the labs were operating while children were in the home.

The professional labs would absolutely not close down due to lack of customers, there would just be even more meth available, more contaminated, with the bonus of hazmat sites peppering communities.