This actually is an office supply I get to obtain from our company's purchasing department for free. I think this costs around $0.11 per piece and can also be sold in boxes.
I actually grew using Mongol Pencils, specifically Pencil # 2, since elementary. And I love using it!
I love it for simple reasons. First, it is really cheap and can be bought in the nearest convenient store. Second, its useful life is longer than other pencil brands I tried. This is because its lead is so durable that it really lasts long before you'll be needing to re-sharpen the lead for a "better" use. Third, its wood body is also durable that it does not break that easily (unless applied with force). Forth, it also has an easy grip, which makes writing better and more comfortable. Lastly, its eraser does not leave dirt on the paper. As if nothing was written in the paper before.
Honestly, the Mongol Pencil has been a very important tool for me - from my school days to my professional career days. And this will continue to become a part of my life as through this pencil I can express myself and I can share myself with others, through writing.