I wouldn't be surprised if prisoners used as "outside" laborers weren't eventually "rented" out to the company bidding highest for their labor. It's unlikely that the prisoners would or will be paid an equivalent wage for their work, as supposedly housing, clothing, meals, and medical care would be taken care of by the prison. So if the going wage was, say, 10.00 per hour, the prisoners could be paid 7.50 per hour because they don't have to pay for things listed above. You needn't be Black to have things like this done to you, and then...well, the Krupp factories didn't pay the "unskilled" workers well.

Better they should be taught a trade whilst "inside" and, yes, paid something for what they produce.