Not to mention that the thing which really matters is impact per calorie provided and, most importantly, there is a 50x range in the amount of calories that pla

Not to mention that the thing which really matters is impact per calorie provided and, most importantly, there is a 50x range in the amount of calories that plants provide per unit of input. So the real advice should be: replace high cost/calorie foods with low cost/calorie foods. Which could mean replacing berries and leafy green vegetables with chicken as much as it means replacing filet mignon with sweet potatoes.