My general food purchasing scheme is to attempt to only purchase the foods I can get at the best prices. If I am shopping and see a 10 pound bag of organic carrots for less than $5 I will buy it and have lots of carrots that week. For example: carrot salad, egg-rolls (carrot filling freezes well), soup, or stir-fry.
I can always buy tortillas for about 3-4 dollars for at least 6 dozen. I freeze them into one dozen stacks and defrost in the microwave until they can be teased apart and finished on a pan.
Some of the best deals I get are at Whole Foods. They often have very good sales on frozen foods. Otherwise I get foods at Costco, a local family market, and Trader Joe's. In the summer I occasionally go to a flea market to get specialty items and seasonal produce.
For instance, pre-made guacamole, if it's actually made entirely from real avocados, is more like $6 where I'm at if you want enough to feed 4 people multiple tacos each -- so twice the price you're quoting here.