the problem is there are a ton of varieties of tofu, and they're all generally around the same price. it seems the silken tofu have around 5g of protein, but some of the extra firm varieties have over 15g protein per 100 tofu, putting it in a much more respectable spot in the bottom middle with the grains and such
No problem! Turns out my Walmart only sells a single package type of tofu so take it with a grain of salt. It's still a cheap and good protein source, but not as dense as an animal or legume protein source.
Is that extra soft tofu? It usually has more protein than that. A pack of extra-soft I have is 8g / 100g, and some other varieties seem to be 10-15 from online sources.
I used a firm tofu, purely because the only other option was over four times the price and the chart specified they used the cheapest price/weight possible. The soft tofu does have about 30% more protein per serving for the same weight, but the price would likely make it an outlier.
Google suggests it's 8g per 100g, which on paper doesn't sound great but a package over here is around 2 bucks for 16oz, roughly 450g. Being conservative we could say 50 cents for 100g.
8, 16, 24, 32 puts us a little under 2 bucks.
That said, tofu is 5 servings of 70cal; the 100g isn't all calories. I'm guessing water? In any case, that eats into your cost effectiveness, putting it closer to the center than near the legumes where it really should be.
Your mileage may vary though. Nuts are great, but peanuts only pull ahead because of how insanely cheap they can be. They're much fattier. Tofus great, though, if you prepare it as intended and not as some meat substitute like many Americans tend to do.