@m0ffx said:
It's not just about 'efficiency' - it's about morality. No doubt it would be more efficient if there was no minimum wage and a great many people were paid so little that they had to go dumpster diving for enough food and live ten to a room. Probably slave labour is rather more efficient than paying workers.
If the workers weren't paid, then how would they afford the good produced?
Capitalism encourages wealth creation through production and consumption - slave labour is against the point.
Of course, as long as the people being paid enough to buy your goods > people actually working in your factories the companies will be fine, but that's another matter...