I have a strict budget for food. I make a shopping list based on needs and save my receipts to track the prices. On the shopping list, I also include the price and that influences my shopping choices. For example, I like Wheaties. The store's price was cut to $2 a box because they over-ordered the UT commerative box so I bought two...regular price was $2.99.
And another item was yeast, I bake bread, 2-3 times a week. Regular Fleishmans Instant in the jar is over $3 for a 4 oz bottle. The store also had institutional vacupack Fleishman's instant for $2.26 a POUND. It will be good for a year which is about the time I will need to buy more. It costs me about $.50 a loaf to make quality bread, including the energy to bake it. I also make pizza dough and other yeast goods so this was an excellent buy.
I also buy store brand items when they prove to be equal in taste testing. Canned Alaskan salmon is all the same, just a few canneries make the canned wild salmon and they stamp it with the same code.
I am so specific that I now shop for my girlfriend because using my price tracking and coupon database, I can save her $4-8 a week.
Oh yes, if you are buying organic, you are getting ripped for the most part.