In the case of mozzarella the savings are somewhat negligible. It depends on the price of the whole milk you buy. At an average $3.50 per gallon around our neck of the woods, factoring about 17 cents for calcium chloride and citric acid (you could use a lemon instead of powder), the total per batch comes to $3.67 or so, which yields right around 10 ounces.
Comparing that to decent quality fresh commercial mozzarella, about $3 for 8 ounces, we’re looking at a total savings of about 8 cents per batch. Maybe nothing to write home about, but it’s a fun hobby, and well worth the time if you enjoy it. Also, the $3 is probably the low end of the range for commercially available fresh mozzarella.
Cheaper to go to the store? That depends on how far away the store is, and your MPG 🙂