America imprisons more people than any other nation in the history of the Earth, and those prisoners' only lifeline to the outside world is the prison phone-system, from which they must make collect-calls. Those calls are billed by Global Tel Link and companies like it, companies that offers kickbacks to the prisons that use its services, which bill prisoners' families more than a dollar a minute, hundreds of times more than free-market carriers. GTL is making over $500M by exploiting the vulnerable families of the most emiserated people in America, and its competitors are making hundreds of millions more. 2.7M American children have to ration their calls to their incarcerated parents, undermining the cohesion of prisoners' families and their ability to support prisoners on release.
This point is made in a long and sad article on prison profiteering by Liliana Segura in The Nation. Worse than phone profiteering is the cruelty of the prison medical contractors, who ration vital treatments to prisoners, leaving them in agony and worse. For example, Correctional Medical Services "discourages treatment for hepatitis," leaving prisoners with hep. C to slide into permanent, profound disability.
These problems are much worse in private prisons, who are guaranteed occupancy by the states and counties that contract with them -- effectively, the government promises to lock up a minimum number of its citizens as a condition of doing business with private prisons. These prisons are not subject to freedom of information requests, are not inspected in the same way as public prisons, and have profit-taking built into their billion-dollar business, meaning that every dollar they spend on care and rehabilitation for prisoners is a dollar they don't return to their shareholders.