About three years ago I bought a small bottle of this 5-culture yoghurt starter and had it mailed to me. I use about a liter of yoghurt a week but I still have about 1/2 the starter left. The small bottle (1 1/4 teaspoons) cost $15.
I discovered that EASYYO packages as starters were much to temperature sensative.. even using a digital thermometer, I got very inconsistant results.
Yes, you can use the small tubs of Denmark plain yoghurt for a starter, but this is MUCH easier and healthier, and even cheaper.
The Dairyconnection starter is easy to use. I fill my sink with HOT water, put in my biggest pot with a lid, also filled with HOT water. I put a pinch of starter into a glass jar (sour marmalade jar rescued from the trash) and load in the cheapest milk with a little instant milk powder (to make it thicker), and then I put the jar into the pot, cover the sink with a folded towel and leave it for 12 hours..(the longer you leave it the more sour the taste). I always get perfect, thick, healthy yoghurt. If you want REAL sour cream, just do the same thing with a liter of sweet cream from Costco (6,000 won). You will have SOUR cream so thick that you can stand a knife upright in it. To make more the next time, DON'T use more bacillus, refill the jar with fresh milk and heat it again! You only need fresh starter if you begin to notice a change in taste of your product.. a taste something like vinegar. That means that another type of bacteria has begun to grow. Just sterilize your jar and start again.