1 plant or many is mostly irrelevant given common sense context. 1 plant just means longer vege requirements and more electricty, which tends to be the biggest cost of all unless you buy a bunch of overpriced soil/nutrient products.
area (size) of canopy and 'enough' medium to provide will produce 50-70g/sq ft. I'm sure there's some sort of physical retrain ceiling as far as how big 1 plant can be grown, but under any common sense context won't be part of the equation. Some phenos may be less and some rarity might push higher, but probably not without supplemental CO2.
from-seed, shooting for 50g/sq ft is an attainable goal even with diversity involved. Much easier to exceed it with clones.
50g/sq foot will excede 1lb in a m^2 by about 100g. Get a clone with a killer yield, well-controlled enviornment with ambient co2 and you might reach 70g/sq ft or more, and might exceed that target production by 300g. This isn't a high-end achievement but does tell you your methods are proficient, and the rest is splitting hairs, anyway.