The raw inputs require delivery contracts from the suppliers and is currently also in short supply. He can’t get his same preferential pricing outside of his supply contracts, or his suppliers may not even be able to deliver it, or they’d require he increase his contract buy.
He may not believe in hiring hourly manufacturing employees on contract without benefits. The amount of time he spends training them and watching them cycle in and out has a cost.
Sure, it could be done. Is it worth it? Obviously not, or he’d be doing it.