How is nutritional yeast made?
Nutritional yeast is not something you can make at home. Nutritional yeast is produced by culturing a yeast in a nutrient medium for several days. The primary ingredient in the growth medium is glucose, often from either sugarcane or beet molasses.

You can make it yourself but you will need an industrial setup and large investment.

It is cheaply available on chinese sites like Ali Baba and DHGate etc from where you can get affordable rates.

You can also track down your country's importer of this product and buy it directly from him thus cutting out the middle men. This is exactly what I do in India and the importer from whom I'm buying originally imports it from China.