I find myself, over the last year or so, having this conversation a lot:
Neighbor/friend: I just love Greek yogurt! We eat a ton of it. I feed it to my kid. But it's so expensive!
Other neighbor/friend: It's not too bad at Trader Joe's. We go through tons of it, too.
Me (biting my lip trying SO hard not to sound like a cultist): I started making my own, and it's way cheaper and really good, and not hard or time-consuming at all.
Here's the deal. Elsewhere on the web, there are lots of recipes for homemade yogurt. One uses a Crock pot, which sounds easy, but my Crock pot is a newer model that gets too hot, and I didn't like the yogurt I made that way AT ALL. Others use powdered milk as an additive to make the yogurt thicker, and I thought it made the yogurt have a weird texture. Some recipes use the oven light to keep the yogurt warm, but my oven has a short, and it makes lightbulbs explode (I realize I should probably address that).
Anyway, it took some trial and error (lots of error) to find an easy, consistent way to make great yogurt, but now that I've done it, you can take advantage of it. And it's basically no harder than heat, cool, mix, pour, wait.
1/2 gallon milk (I use organic 2%)
1/2 cup yogurt with live cultures (I use Fage to start*)
You will also need a large saucepan, a thermometer, two quart-sized containers (I use glass jars, but Tupperware or whatever you have works), an insulated bag, and one more unlikely-to-melt container. Plus spoons and junk. A funnel is nice, but not necessary.
First, pour the milk into the saucepan and heat it over medium heat, stirring occasionally, until it reaches 180 degrees. Take it off the burner.
Second, wait.** Boil some water while you're waiting. For real.
Third, when it has cooled down to about 110 degrees, pour some of the warm milk into a bowl with the 1/2 yogurt and mix them together. Then pour that mixture into the pan of warm milk. Now, pour all that milk-with-yogurt-mixed-in into your jars or Tupperware and close them up. Put them in the insulated bag.
Fourth, pour the boiling water in the non-melty container, seal it up, and add it to the insulated bag, too.
Fifth, wait some more. Between 7 and 10 hours, I'd say. Overnight is probably fine. The deal is, it's not so sour and yogurt-y at seven hours, but it's thin. At ten hours, it's thick and Greek-y, but it's pretty sour, too. I prefer thick and sour, so I usually let it go ten. You can always check yours and see.
When it's ready, just throw the jars in the fridge. I've seen it recommended that you whisk them rapidly before doing so, but in my experience, it doesn't make a damn bit of difference.
Now here's how it rolls out financially: I spent $3.89 on milk and got two quarts of yogurt. (See the notes below for why I'm not including the price of the Fage.) That's approximately the same as 3 1/2 500 gram containers of Fage, which costs about $5. So that's a steal if you're buying bulk containers of yogurt, and the single-serving yogurts are about the same (18 bucks).
Sure, I put a little work in, but the truth is, even with washing the dishes, my total time contribution was less than ten minutes (pour, stir, mix, pour, put in bag, take out of bag).
Now if you're really into your yogurt being thick, Greek-style yogurt that you can cut into like custard, this is probably not quite it (it's almost it), but you can drain it (in a clean cloth dish towel over a bowl) to make it thicker if you really want.
And now for my serving suggestions! Add some honey, maple syrup, or jam. Add some granola or Kashi cereal. Add cucumber, salt, garlic and dill for tzaziki! Use in place of sour cream on taco night. Throw in fresh or canned fruit. I eat yogurt as my snack almost every single day (two quarts lasts about two weeks for me), and I never get bored, because one day, I'll throw in raspberry jam, and the next it'll be maple syrup and Kashi, the third day I'll put in a diced canned pear, and they'll taste like completely different snacks.
If I've convinced you and you try it, just beware of social gatherings, because you're going to want to spread this news like the clap.
*I use Fage the first time I make a batch, then the next three or four batches, I just use my own leftover yogurt to start the new batch. (That's what you're seeing in the pictures.) Then I'll start with Fage again, just to make sure the cultures are still, you know, live and active.
**If you have limited time and don't want to wait (depending on how hot your house is, it seems like this takes most of an hour), you can speed it up. Stop up the sink with a drain-pluggy-thing. Dump a bunch of ice in. Run the water so it's three or four inches deep. Put the saucepan in the water bath, stir it, and watch the temperature closely, because it has a tendency to drop really fast. When it gets to 110 degrees, proceed with the next step in the recipe.