It's pay. It's always pay.
You gave a range so I'm guessing the lower end is starting out, why take that when nearly every entry level job, with far less demand, pays about the same?
Start your pay at $45/hr and people will flood in. If they aren't, it's because the factory is too remote for population to get to. Put that factory in any mid to large midwestern city and it'll be flooded with applicants.
How do I know? About an hour south of Louisville, Amazon keeps building giant warehouses and hiring workers, and people fight over those jobs. They don't pay half of that.