It really depends on where I shop and how many "specialty" products I am buying. I do cook a lot from scratch, I soak/cook my own beans, make my own granola, etc.
As far as vegan vs. lacto-ovo vegetarian, I have found that vegan is actually a bit cheaper. Soymilk is about the same price as the Organic Valley cow's milk I was buying. But what really got me, price-wise, was buying organic cheese, cottage cheese, sour cream, cream cheese, and eggs. When I removed those items from my food bill it actually got quite a bit cheaper. Now that we're off dairy and eggs again, we are eating more tofu (which is WAY cheaper than organic cheese!) and beans.