We managed to save about 50% off the cost of formula by making our own. A can of goat milk powder (Myenberg) costs ~ $10 and makes 3 quarts. Before 6 months we made sure the formula matched breast milk, using a spreadsheet--I'm working on a web app!--but let's say after 6 months it's fine to feed straight goat milk. Assuming a quart (32 fl oz) per day, that's about $3.33 per day, compared to $6/day for Enfamil ($27 for a tub that makes 18 cups).