According to a report by Peter Wagner and Bernadette Rabuy Following the Money of Mass Incarceration, about the Prison Policy Institute of the USA, the system of mass imprisonment costs the government and families of those involved with the judiciary at least 182 billion  dollars a year.
The costs associated with the prison system include:
- 80.7 billion dollars corresponding to public correctional agencies, including prisons, detention centres the costs of probation periods.
- 5.8 billion dollars on trials.
- 63.2 billion dollars on the police (this only incudes expenses linked to penal law).
- 12.3 billion dollars corresponding to healthcare within prisons and detention centres.
This study is regarded as a first step towards a better understanding of who benefits most from the overall US prison system and, consequently, would be able to resist any possible reform in this area. However, the authors believe that some costs have been underestimated, as they would have little relevance  or may even be unknown.
Nevertheless, they stress that the corporations of private prisons would not be the only ones to benefit from a large-scale imprisonment policy.
The United States has a federal penitentiary system, 50 state systems and thousands of local government systems. At times, these systems work together, although they often don’t; and if one focuses only on the national scene, the importance of political decisions at state and local level could be hidden. For example, while state government expenses account for most prison costs (57%), local government represents almost a third of the total expenditure (32%).
Local governments are, to a large extent, applying state laws, and the local discretional policies of detention and bail could have an enormous influence both on the state budget and judicial results. For example, over half (13.6 billion dollars) of the cost of running local prisons is spent on detaining people who are finally not sentenced.
Almost half of the money spent on the running of the penitentiary system is used to pay the personnel. This is an influential group which sometimes prevents reform.
Other noteworthy elements are:
- Public/private system: The criminal justice system is essentially a public system, with private prison companies which exercise as an extension of the public system. The government wage bill for prison staff is 100 times bigger than the profits of the private prison industry.
- Although the constitution demands a court-appointed lawyer for those who cannot afford one, the system only spends 4.5 million dollars on this right. And, over the last decade, states have reduced this figure, although the number of cases has increased.
- Food and healthcare for 2.3 million people –for a population bigger than the 15 different states– is very expensive.
 In the US, “billions” refers to thousands of million of dollars.
 In this study, all cost below a billion dollars have been overlooked, due to the difficulty involved in calculating all expenses correctly.