WHO published in May this year Global costs and benefits of drinking-water supply and sanitation interventions to reach the MDG target and universal coverage by Dr Guy Hutton. Here’s the Overview from the WHO webpage for the report:
This report updates previous economic analyses conducted by the World Health Organization, using new WSS coverage rates, costs of services, income levels and health indicators. Benefit-cost ratios (BCR) and costs are estimated to meet the MDG drinking-water and sanitation target and to attain universal access of basic services. Rural and urban areas are analysed as separate targets. The analysis utilises WSS coverage definitions of the JMP (WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation).
The bottom line is: The benefit-cost ratio for the necessary interventions varies from 2.8 in the SSA region to 8.0 in E. Asia. The global economic return on sanitation spending is US$ 5.5 per US dollar invested.
A good, if somewhat exhausting, read! Read the Executive Summary at least.