Many researchers have noted that most prison employees are paid only a small percentage of what non-incarcerated workers earn. This imbalance serves to drive wages down for all workers because companies contract with prisons to obtain cheaper labor. In many cases, US prisoners earn far less than workers in offshore manufacturing sites. This line of argument supports paying prisoners the same wages as non-prisoners because of economic justice for all workers, as doing so would prevent employers from moving jobs into the prisons.
Another argument in favor of paying minimum wage is legal. Rather than thinking about what prisoners are allowed to earn, we might consider what the prisons are required to pay. Wages are established by federal and state law, so any business that fails to pay those wages to people just because they are incarcerated can be considered to be violating those laws. This establishes a contradiction in that the very people who are charged with enforcing laws are themselves breaking the law.
Dignity is another reason in favor of paying a fair wage. While prisoners have almost no expenses while residing in the prison, they often have outstanding debts or responsibilities such as childcare, including court-mandated child support. Incarceration thus increases the burden on innocent members of society, including children and on businesses such as banks to whom the debts are owed. Monies earned while working in prison could be automatically directed toward those obligations.