For a little while I was tracking the exact unit cost of the grocery items we bought just so we would be more price-aware, but I only did that for like a month. It paid off tremendously, though, because now I know when something is too expensive / a better buy elsewhere.
My budget (household and groceries) is consistently $100/mo for one person. In October it came to $70/mo -- I think because we were out of town for 4 days. I am vegetarian, but we don't buy alternative products. Sometimes we'll get tofu, but if I want veggie patties, I make them at home (surprisingly easy and also you can freeze them).
Probably the big difference is that we don't really buy processed anything. No juice, no chips (only rice crackers -- which has 2 ingredients), no cookies, no hummus, etc. Processed foods cost SO MUCH. If we really want a snack, we just go the extra step to make it (and that way it controls overeating of junk food too). We still don't make our own yogurt...