I don't keep a price book.
But I should! I try to keep in mind all the lowest prices I know I can get for this item and the other, but I know I don't always succeed. If I would just write it all down, I know I could keep a few more dollars in my hands and out of the supermarket's every week.
I get ahead of myself. What's a price book?
Amy Dacyczyn explains this brilliant tool in her brilliant compendium, The Complete Tightwad Gazette. Look at your grocery list. Take a notebook (or a spreadsheet) and make one entry for each item in your grocery list. (You don't need to take an inventory of your pantry and list every single item there; start with this week's grocery list, and add new items as they come up.) While shopping, note the date you bought each item and what price you found. Note the price per unit or by weight, and note the package size. Note which supermarket or big-box retailer you bought it from. And repeat all these notes every week, especially noting prices as they rise, and making sure you writing down the date.
Do this for every item. Not just grocery foods, but also household necessities like toiletries and cleaning products; home maintenance hardware like furnace air filters and lightbulbs; and even some clothing items like sport socks and those plain white undershirts that come in 12-packs. Everything! You hear me?
After a few months, set a couple of hours aside and look at the data you've gathered. Some prices are steadily going up; some cycle every few months or twice a year. Sometimes the big-box retailers don't actually have the best price. In a separate master list, or by writing in different colored pen on the entry for each item, note the lowest price you see and how frequently that price cycles around. At this point, you have a very powerful tool for your pantry planning. You can now stock your pantry in an awesomely efficient way: by buying what you need at the lowest price possible in a quantity that will carry you to the next time that lowest price appears. Brilliant!
Here's the Rowhouse Livin' example. At my local supermarket, the regular price of the pastawe prefer for quality reasons is $1.39/lb. This is an objectively ridiculous price; and sometimes it goes up even more, and some of the varieties have been appearing in 12-oz. boxes rather than 16-oz. I hate the "grocery shrink ray." But the brand we like does cycle down to $0.99/lb. on a regular basis. I call this number my price point, and whenever I see our favorite pasta at that price, I snap up as many boxes as I can carry. (The Rowhouse Livin' price point for family size boxes of Tastykakes is 2 for $4.00. This unfortunate blogger is paying too much!) But more importantly, and this is the only way you can get the most effectiveness out of this tool: I never buy pasta at a price higher than that point, ever. Even when my pantry is empty of pasta.
What should your price book look like? Dacyczyn gave a description in her Gazette that I don't recall offhand, and my copy of the book is at a friend's house so I can't look it up. But it could be just about anything: a small loose leaf notebook, a classic marble composition book, an ordinary spiral-bound notebook, or even a stack of index cardsand a rubber band. If loose-leaf, use one piece of paper for each grocery item. If a comp book or spiral-bound notebook, use one page or one half-page per item. If index cards, use one card per item. The way you create this tool isn't terribly important; do what works for you, though it'll be easier to use if you can alphabetize items by name and perhaps organize by store. What's crucially important is that you don't ever stop using it. Your price book is a dynamic document, and prices are always going to change.
Hop to it! Right now, you probably have kicking around the house an old, half-used notebook you can repurpose for a price book. Within six months, and definitely after 12 months, you'll have a completed tool for effectively controlling your food and household purchases budget.