I have tried a couple different instructions, and I like the ones from Raising Olives the best. We like yogurt but I will only buy unsweetened, no pectin or thickeners, plain yogurt- which can be expensive. We use one large container for a round of breakfast smoothies and it is between $2-$4, depending on what sales I get and if I decide to get organic (which I prefer). Using milk from Sam's Club and a small container of Organic Brown Cow Greek Yogurt for the starter, it costs around $0.75 per quart. If I remember to save my own starter culture it is even less than that.
We don't drink a lot of milk, but we can easily use 4 quarts (a gallon) of yogurt in a week for breakfast smoothies and yogurt and granola. I do like to make my own granola as well and have had good success with the recipe in Whole Foods for the Whole Family, but it has quite a few additives/flours that I don't love. Lately, I have been using the Maple Nut Granola recipe from Clean Food as it is naturally dairy free and gluten free with the right oats.