When it comes to price, that's what government subsidies do for the cow's milk and high demand does for the oat milk. Although, I've seen Temple Grandin's methods live and a milk farm with milking robots basically runs itself (all cows just walk to the robot to be milked and the robot finds the teats with a bit of computer vision).

But yes, other than a good soy milk, most of plant-based milks are just empty calories.