In the past, the way of exchanging soybeans for tofu in rural areas was mainly in the form of barter, from which tofu shops could earn the difference.

From an economic point of view, taking tofu as an example, a catty of soybeans can produce 2.5-3 catties of old tofu or 4.5-5 catties of tender tofu. If you sell 100 kg of soybeans at the market price one day, the gross profit can reach 400 yuan, and the gross profit rate is 133%.