Bitcoin value compared to land

I always think about how bitcoin future wd look like. Today I got this idea to calculate how much is 0.1 bitcoin(avrg people hold amt) in land if we assume 21million equal to total usable land in world. After some maty it equals to 12acres, which is not that high. I expected a larger number. The number I used as total usable land is from google. I think the real number wd be even smaller. Now I have questions like maybe we late to the bitcoin game. ????