The average cost to make a generic bottle of dish washing soap is about 20 cents. The actual cost to make a bottle of name-brand Dawn dish washing liquid is not publicly known or available.
Most people have the supplies and kitchen tools they need around their home to make dish soap. The necessary tools and ingredients include solid or liquid castile soap, water, lemon juice or white vinegar, a large bowl, a sharp knife, a funnel and empty bottles. Another benefit to making homemade detergent and liquid soap is that it cleans your clothes and dishes using ingredients that are less toxic to the environment.