Certainly if you have sufficient storage, it's possible to buy meat in bulk quite cheaply, some of which might even be cheaper per kg (or per calorie?) than many vegetables, but if you stick to in-season vegies and cook them sensibly (into dishes that last a while), on average they're still going to be cheaper than meat. Plenty are in the order of $1-$2/kg in Aus. (potatoes, onions, pumpkin etc.) - I don't know any meat that cheap.