AFAIK it's voluntary, no? Also, given the choice between working 8(?) hours a day, or sitting staring at a cell wall for the same hours, which would you pick? (I'd pick the work)
I'd absolutely choose staring at walls to cleaning toilets for $5 a month.
But if it's completely voluntary, and you won't face any direct nor indirect retaliation for refusing, then I have less of a problem with it (it still distorts the labor market when they take jobs from people not incarcerated, and the taxpayers are the ones subsidizing those jobs.)
You still need stuff from the commissary though, so unless someone is putting money in your prison account you'll need to get money somehow. I'd rather clean toilets for $5/month than some of the other alternatives (I don't know what they would be but I imagine they're not pleasant).
But if it's completely voluntary, and you won't face any direct nor indirect retaliation for refusing, then I have less of a problem with it (it still distorts the labor market when they take jobs from people not incarcerated, and the taxpayers are the ones subsidizing those jobs.)