The "wages" are typically something like 25 cents per hour, often much less than that. The work is mandatory, and sentences can be extended if you refuse to work, so they effectively are sentenced to labor.
What little money they get they immediately give back.
Inmates are charged anywhere from $0.06 to $0.25 per minute for phone calls.
Prisons spend less than $2/day per inmate on meals,
barely enough for sustenance,
so many inmates supplement by purchasing from the prison commissary.
If that's not bad enough,
prisons in 40 states are so-called pay-to-stay,
charging prisoners for their accommodations.