> the price of veggies would obviously go 10x

What makes you think so? My naïve view is if people eat soy instead of an animal eating the soy there's less total soy needed, by a fair margin. The pasture animals are a different deal but that represent a tiny proportion of consumes nutrients around the world.

Moreover, people that transition from omni to veggie diet don't eat 10x more veggies (with exceptions of course), even if grains and pulses are counted as veggies. We can't eat as much as what the livestock eat themselves.