A lot of headcount in a factory is support staff. A lot of it is the management in the office (you do not need two plant managers, two plant controllers, two production supervisors, etc). Then you have the costs to keep the place open: real estate taxes, heat, water, sewer, etc. And two countries worth of safety, environmental and health regulations to keep up with. Even on the hourly side you can have savings. Depending on the size of the operation, sometimes a 25% increase in workforce on a shift can make 2X the product. You will get more efficiency from the warehouse too.
Unfortunately, throughout my career, I had to close a lot of facilities. The real savings come from closing a plant, rather than pruning around the edges and improving productivity (often for the reasons above).