"A limited number of evaluations in our review discussed the costs and benefits of adult drug court programs. Four evaluations of seven drug court programs provided sufficient cost and benefit data to estimate their net benefits (that is, the benefits minus costs). The cost per drug court program participant was greater than the cost per comparison group member in six of these drug court programs. However, all seven programs yielded positive net benefits, primarily from reductions in recidivism affecting both judicial system costs and avoided costs to potential victims. Net benefits ranged from about $1,000 per participant to about $15,000 in the seven programs. These benefits may underestimate drug court programs' true benefits because the evaluations did not include indirect benefits (such as reduced medical costs of treated participants). Financial cost savings for the criminal justice system (taking into account recidivism reductions) were found in two of the seven programs."
United States Government Accountability Office, "Adult Drug Courts: Evidence Indicates Recidivism Reductions and Mixed Results for Other Outcomes," (Washington, DC: Feb. 2005) GAO-05-219, p. 6-7.