Not really super surprising— the volumes are way lower and there's less subsidizing going on. On a grocery store shelf here in Ontario, you can get 4L of 2% regular milk for $5. But the Earth's Own products, which include oat and soy milk? Those are more like $6 for a single litre.
As a parent of young kids, we easily do 1L+ of milk per day, even when we drink water as our meal beverage. It goes on cereal in the mornings + a glass before bed + it's an ingredient for certain meals (think baking, cheese sauces, that kind of thing).
I used to make yogurt and cheese as well, but it wasn't really cost/labour effective to do so, even with milk being as cheap as it is.