1. Low cost of sunflower seeds: Black soil sunflower seeds are a relatively cheap food with low production cost. In addition, because sunflower seed is a common food, its supply is relatively sufficient, so the price is relatively low.

2. Simple production process: the production process of black soil sunflower seed oil is relatively simple, and does not require too much equipment and investment. In addition, due to the high oil yield and high production efficiency of sunflower seed oil, the production cost is further reduced.

To sum up, black soil sunflower seed oil is cheap because of its low cost and simple production process. However, this does not mean that its quality is not good. Black soil sunflower seed oil is also a nutritious edible oil, which can meet the human body's demand for fatty acids.