Derek,
Thanks for visiting our site and in response to your question; "prisons are a business that provide employment to large numbers of people. They employ inmate labor to produce materials which is then sold to the public at reduced prices since they are able to pay inmates a pittance for their labor."
Please read the 13th amendment
Amendment XIII (1865)
Section 1.
Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Section 2.
Congress shall have power to enforce this article by appropriate legislation
Now let's take into consideration that for every offender released back into society several service providers are needed. For everyone returned to prison the courts and other legal services are needed.so once there the cycle begins anew.
What's really needed is a way to reduce the recidivist rate.