I don't eat yogurt.
I refuse to eat active bacterial cultures.
And therefore I especially won't eat Activia, because it contains three or four times the active bacteria.
If you want to get yogurt cheap, buy a pack of yogurt and a gallon of milk. Maintain heat at around 90 degrees. Mix. In a week, you'll have a gallon of yogurt.
It will taste like normal yoghurt, because that's what it is.