Anecdotally, UK, the cheapest yoghurt (believe me, I have researched!) just dropped from £1.10/l to about £0.7/l - anomalous considering the rampant groceries inflation we have, but there it is.

Milk is about £0.64/l, so roughly equivalent if you add in the cost of heating it.

However, the price for live yoghurt is a different story - much more expensive, which is why I have recently started making my own.