COGS typically includes payroll for employees whose labor is directly tied to production but doesn't include 'overhead' employees and other categories like rent

COGS typically includes payroll for employees whose labor is directly tied to production but doesn't include 'overhead' employees and other categories like rent / legal / sales / marketing. The best way to think about it: "If we had 0 sales, would this expense still exist?" If it wouldn't exist, it's COGS.