Well if prisoners are digging holes, you can calculate how much it would cost to pay them minimum wage but it doesn’t mean that the owners of the system benefit

Well if prisoners are digging holes, you can calculate how much it would cost to pay them minimum wage but it doesn’t mean that the owners of the system benefit from the holes. The relevant question is how much money is made from the output of the prisoner labor. And then, is that amount enough to plausibly provide an incentive to, say, apply political pressure to get more prison labor, as opposed to just being a grift on top of the prison population that would exist anyway without the presence of the grift.