This report analyzing the benefits and costs of substance abuse treatment in South Dakota concludes that substance abuse treatment in the state costs an average of $1,382 per-client but benefits average $11,653 per-client, resulting in a benefit-cost ratio of 8.43 to 1, or $8.43 for every dollar spent on substance abuse treatment.  The report provides a detailed breakdowns of those cost estimates. 

From the report:

Substance abuse has a major impact on the child welfare system in this country. It is estimated that nearly one-tenth (9 percent) of children live with at least one parent who abuses alcohol or other drugs.

Children of substance abusing parents often have multiple problems and are more likely to have poorer physical, intellectual, social, and emotional outcomes and are at greater risk of developing substance abuse problems themselves. Data indicate that abused or neglected children from substance abusing families are more likely to be placed in foster care and are more likely to remain there longer than maltreated children from non-substance abusing families. Studies have shown varying results, but between one-third and two-thirds of child maltreatment cases involve substance abuse. In a recent survey by the National Center on Child Abuse Prevention Research, many (85 percent of States) reported that substance abuse was one of the two major problems exhibited by families in which maltreatment was suspected. One study estimated that of the more than $24 billion States spend to address different aspects of substance abuse, $5.3 billion (slightly more than 20 percent) goes to child welfare costs related to substance abuse.

Full report: Substance Abuse Treatment Produces Savings in South Dakota (PDF | 50KB)

Leonardson, G. R. (2005). Substance abuse treatment produces savings in South Dakota. Mountain Plains Research for the Division of Alcohol and Drug Abuse, State of South Dakota.