Creating My Own Price Book

In my on-going attempt to spend as little as possible at the grocery store I am considering taking Mrs. Momma's advice (thanks Heather!) and starting my own Price Book.

I have, on occasion, written down the price of something at one store, say Kroger, if I was going to Wal-Mart next because I knew that if I found it more expensive at Wal-Mart that they would price-match Kroger's price (or whatever store it was cheaper at). So in a way I've done something like this before. It just never occurred to me to keep a running list on several items. I know it will take time, but with a family of six (and two of those six being growing boys with ever-increasing appetites) and continual price increases I want to make sure I'm doing everything I can to be a good steward of what God blesses us with financially.

Do any of you have your own Price Book? Is it worth it? Does it help you save?