If those workers didn't automatically get a pay raise (and I'd be surprised if they didn't, but for the sake of argument, let's say they didn't), there would be, at the very least, pressure on that employer to raise his wages, because he no longer has the hiring advantages (namely, being selective) that come with paying 2x minimum wage. The employees that wanted to work for him for the higher pay now have more options at that pay tier, so if the factory owner wants to retain those employees (or hire employees of a similar caliber), he'll need to raise his pay rates in order to be more attractive.