The problem with this is that allowing prison labour to be cheaper than free labour puts competitors out of business and gives incentives to the state and business lobbyists to arrest more people for the sake of profit instead of reformation or containment.
There are two different approaches to this that are the same on the outside. Paying the workers more is one, the other is charging a minimum for their time, but X% of their earned wages go to some other entity (the government directly, victim support, community projects). This would help the issue with competition, but not necessarily the other issues. It also doesn't touch the moral aspect of how much people should get paid.
Get rid of private prisons, period. You can even keep the same business model except instead of the profits going to a corporation, the system is run as a non-profit government entity and the workers are actually paid a fair wage.
As it is right now, we have slaves working to enrich CEOs, board members and investors.
You can even keep the same business model except instead of the profits going to a corporation, the system is run as a non-profit government entity
Which is exactly what's happening in this case. There's no private corporation, it's a governmental division, yet the inmates are still paid a pittance. Maybe you should review your preconception of private industry vs government.