Few years ago, based on what I read at some frugal living blogs, I started a Price Book but, I am not that organized. Yes, I make a budget, yes, I save money on a monthly basis but keeping a Price Book is a bit of a stretch. I do have a good memory though and I use that to my advantage.
I know the unit prices of all sorts of detergents I use, paper goods, olive oil, milk and a lot of other staples. So, while grocery shopping I always compare unit prices and if there is a real good deal of something I regularly use, I stock up on that item. This works for me.
Mom is currently with me until mid February or so but, I remember her mentioning that she was low on dishwasher tablets. So, the other day as we were walking the isles of a supermarket, I noticed a very good deal on dishwasher detergent and we bought her a large pack. She laughs at me for remembering such stuff but again, it works for me!
Few weeks ago I snatched up body washing liquids at half price. They came in small bottles but the unit price was cheaper than the large bottles. Larger containers do not always mean economy. Also, I like it better when I have small bottles of a variety of fragrances instead of having to wash with the same thing for months. Another thing I have noticed is that I use liquid cleaning products more sparingly if they are in a smaller bottle. So, even when I buy large bottles due to a good price, I pour the contents to smaller ones.