Cost Benefits:

• Money saved by not buying off-site compost for landscaping (Compost costs approximately $40/CY installed)
  
• Reduction in municipal energy costs used to treat human waste (Municipalities spend millions to tens-of-millions of dollars annually on treating wastewater)
  
• Savings in stormwater/sanitation fees and taxes. According to Seattle Public Utilities, the typical 2011 residential sewer, water, and drainage fees per month are about $106.  Composting toilets can reduce water use by 20-50%.
  
• Greatly prolonging the life of septic systems and reducing pump-out and maintenance costs (about $200-300 per year).  This is most applicable in rural settings.
  

Studies have shown that owners of a composting toilet can expect it to pay for itself in less than 2 years.

Upfront Costs:

• Commercially available composting toilets range from about $1,000 - $1,500 for a single full time user to $4,00-$10,000 toilets that can handle a large household.  Do-it-yourself systems are significantly less expensive but may face higher scrutiny during the permitting process. 

• Composting toilets at the visitor center for Frank Lloyd Wright’s Fallingwater house take care of 120,000 visitors per year.  This toilet costs $10,000
• Conventional toilets cost about $300, and incur monthly sewage fees for the life of the toilet. 

• Costs in inspection fees and code reviews (this also applies to conventional systems)
  
• Costs in startup compost additives (such as peat, straw or sawdust)