Review of Oats Original Unsweetened - Only Earth by vasundhara

I got this unsweetened oat milk pack as a sample. The taste was naturally sweet and would probably go well with coffee. I would love to try a latte made with it.
Having said that, I think it's a bit pricey to be included in regular grocery.
Can someone tell me why oat milk is more expensive than other types of plant milk like soy when oats are really cheap?