[nightski]

That's not exactly true. I do a lot of work for agricultural companies. One such company is a huge supplier of animal feed. Their products are the by-products of sugar production. Raffinate, Betaine, Molasses, Beet Pulp Pellets, etc... These products are very shelf stable and cheap. But they are not the main crop. Sugar Beets are not grown for these by-products.

In addition, grazing animals require no such feed. Grass fed beef is a thing, and it's price is on par or even quite a bit cheaper than fake meat.

[Djvacto]

However, even if the animals require no food to be purchased by the farmer, there is still an environmental cost in the land being used, plus the opportunity cost of other uses of that land.

Not all land used for grazing can be used to grow plants, true, but in the cases it can be, you're using that land at a 10% kcal efficiency, so to speak.