Well we're talking about morality, so is it morally wrong? I'm fairly sure you'd say conscription is morally wrong, but is jury duty morally wrong? I'm not sure a government can continue to exist without forcing people to work in one form or another.
Jury duty is an interesting question. I’m not a huge fan of the jury system, although it may be the best of bad alternatives. Maybe there’s no good way around this one.
I get that you’re trying to trip me up (and succeeding a bit), but penal labor isn’t difficult or borderline or anything like that. It’s a straightforward “we can make money by forcing that person to work, and it’s not illegal.” There’s no justification beyond, they’re a criminal so they deserve it. Obviously, criminal punishment has to involve violation of certain rights, but I don’t see any reason for it to involve violating this right besides liking money and wanting more of it.
“Covering costs” is just a different way to say “we like money and we can get some by enslaving that person.” It’s not a moral justification for anything.