Making unsweetened yogurt (plain or greek style) is surprisingly easy. It takes about 1/2 hour and I leave it overnight (in a cooler) to 'develop'.

I would recommend more people try it. It's generally better than store bought plain style yogurt and super-cheap.

I can get a gallon of milk (on sale, non hormone BST stuff) for about $2 (in CO, US). That will yield the same in yogurt (4 quarts.. I use quart mason jars).