Chasson, Harris, and Neely, in a recent issue of the Journal of Child and Family Studies (2007),  reported that: 

The financial implications of the increased prevalence of autism, though rarely discussed, will be extremely important to society. We compared the costs associated with 18 years of special education to the costs associated with the implementation of an average of 3 years of Discrete Trial Training as an Early Intensive Behavioral Intervention (EIBI) in an effort to minimize the need for special education. Our results indicate that the state of Texas would save $208,500 per child across eighteen years of education with EIBI. When applied to the conservative estimate of 10,000 children with autism in Texas, the State would save a total of $2.09 billion with EIBI. Implications for taxpayers, policymakers, and treatment are discussed.

(Abstract: Cost Comparison of Early Intensive Behavioral Intervention and Special Education for Children with Autism, 16, 401-413)

An earlier article by Jacobson, Mulick, and Green in 1998 looked at the cost-benefit of EIBI for young children with Autism had a broader scope in its review of overall costs.  Research has shown that without effective intervention, most people with autism and other pervasive developmental disorders (PDD) require lifelong specialized educational, family, and adult services, at a total cost that is estimated at upwards of $4 million per person.  The overall average savings from implementation of EIBI are estimated to range from well over $1 million to over $2 million per individual across their life span.

Jacobson, J.W.,Mulick, J. A., & Green, G. (1998). Cost-benefit estimates for early intensive behavioral intervention for young children with autism: General model and single state case. Behavioral Interventions, 13, 201–226.

Another report on the cost savings of implementation of EIBI comes from Ontario, Canada.  "The Cost-Effectiveness of Expanding Intensive Behavioural Intervention to All Autistic Children in Ontario."  The increased awareness of IBI and its high program cost have made the financing of IBI and its cost-effectiveness relevant concerns for governments.  The cost of expanding IBI to all autistic individuals (ages 2 to 5) is small (less than 10% of total costs) compared to the significant cost of educating and supporting semi- and very dependent individuals over their lifetime.

Sanober S. Motiwala, Shamali Gupta, Meredith B. Lilly, Wendy J. Ungar, Peter C. Coyte Department of Health Policy, Management and Evaluation University of Toronto, ON Vol.1 No.2, 2006

The Canadian government commissioned a cost-benefit analysis of providing cash grants to parents in order for them to hire competent EIBI/ABA in-home providers versus the direct provision of services through the provincial government.  The Auditor General’s Report [November 4, 2004] revealed the following comparative: DSO vs. DFO Costs [Page 13 of the report] The Governments Direct Service Option (DSO) averaged from $48 to $92 thousand per year by  providing 23 hours of services weekly.  Costs per hour of Government provided direct services was between $82.00 to $136.00 (averages at $109).   IN comparison, the cost of parents hiring professionals, the Direct Funding Option (DFO), was from $21 to $36 thousand per year for  providing 25 hrs of services weekly.   Cost per hour between $22.00 to $32.00 (averages at $27.) This represents an average cost savings of $82 per hour!  (All figures are in Canadian Dollar amounts)

The Chasson, Harris, & Neely article can be found online at: 
http://www.springerlink.com/content/52q6k240l5125294/fulltext.pdf

The Motiwala, Gupta, Lilly,  Ungar, & Coyte article can be found online at: