I don't think it is as simple as just higher more people. I have seen several companies sink by trying that. There is an art to expanding without losing what made it successful to start.
I work in pool/landscaping, doing the actual sales/install of the projects. So while different than manufacturing, we have some of the same issues. We need more people and am slammed to the point that we can't keep up. I can respond to about 4-5 new clients a week. Right now I'm sent 6-8. So I'm looking 3-4 leads a week, just by not being able to respond to them.
But where do we hire qualified, experience people to do the work? When the market ramps up, the only people looking for a job are inexperienced or lack the skills to interact with people. Yes, there is entry level positions, but you still have to bust your butt to do it, namely running a wheelbarrow back and worth all day. We can easily get a new person to fill any job, but they won't be any good for a year or two. In the meantime, they cause as much, if not more, problems than before they came around. I have been at a few places that try to have people fill spaces and the company loses exactly what made it successful. Having key people in the right places is important. Certain businesses, including specialty manufacturing, isn't easily scalable. So you can't just ramp up production without losing quality or profitability. I worked at a company that made more money selling 2.5 million worth of landscaping than it did at 5 million dollars. They tried to expand too quickly and they are now out of business.