Magic Window Cleaner: No towel drying, no streaks, no spots! Fill an empty spray bottle with: 1 tablespoon liquid "Jet Dry" 3 tablespoons blue Dawn dish soap Fill to the top with water, shake. Spray your wet windows with the solution, scrub all over with a sponge, immediately wash off, that's it! by Titanium Taurus
I haven't actually done the math, but this web site reports that this recipe works out to about 4 cents a load. A 5 gal batch will last me between 4 - 6 months (less during football season). It's good at removing sweaty, football smells too.