For kids who liked getting out the Bunsen burner during chemistry class.
I've been making my own Greek yogurt, mostly using information I got from this cooking blog post.
It's really a simple process. I'm going old school, making it from skim milk, but here's an old Tnation post on the topic, for anybody who's interested (It was locked down so I started a new thread). The link here shows somebody who bought regular yogurt, then strained it to make Greek yogurt. http://tnation.T-Nation.com/free_online_forum/diet_performance_nutrition_supplements/homemade_greek_yogurt
This is really just for people who like to know how things are made, or like dinking around in the kitchen. The cost analysis may or may not be worth it to you, depending on how much you enjoy this sort of thing.
It takes about 1 Gallon of Skim milk to make between 4-6 cup servings of Greek Yogurt. It's dense, so most of the liquid gets strained off. Yields will vary depending on how long you strain it, and how firm it gets during incubation, so you can figure your costs according to milk prices in your area. I pay about $3.00 per gallon of hormone-free skim milk, which will yield 4-6 servings of protein packed Greek yogurt. Of course, I need a couple of tablespoons of starter to make a batch of yogurt, and then there are some energy costs for heating. No clue what those are, but it's not a lot.
Yogurt costs in Southern California:
Fage individual serving size yogurt is about $2.19 per container (1 cup).
Fage 35.3 oz container (4 servings) range from $7.99 at my grocery store, to $5.19 at Costco.
Edit: The Fage website says they use a 4:1 ratio to make their yogurt, so 1 Gallon of milk will make about 4 cups. If you want to try to replicate their macros, you can strain it down using that as a guideline.