You don't seem to be able to buy alternative milks in large volume. I think it's fair to compare against the $1.87 per litre you pay if you buy a 3L countdown milk.

Oat milk is what I'm most interested in, I generally don't like the taste of soy, almond, or coconut even when they aren't milk. I quite enjoy oat milk though (but I also like oats). You just have to go into it knowing it won't taste like cow milk.

However even at $4 a litre it's still more than twice as much as the cow milk. You're right though, not as much as I thought.