Loss Leader - take advantage of it
Grocery stores are famous for offering loss leader products in their weekly circulars. That's the industry that started the trend and coined the phrase. They are products offered at or below cost to lead you (the one with the money in their pocket) into the store.
Notice that grocery stores usually offer only a few really good deals in the form of these "leaders" in their weekly ads. That's because they believe that's all they need to offer in order to lure you into the store.
Their thinking is that once you're there, you'll buy more of their stock that isn't on sale. That's the idea behind a loss leader. It doesn't always work, but generally it does. Stick to your list and buy what you know is on sale, but don't wander around to see what else they have.
If you want to save money on groceries, then you might want to visit all the nearby stores offering different "leaders" that you want and can use. No sense buying something that you won't make good use of.
While visiting many of the nearby stores, it would be a good time to do other errands as well so you make one combined trip to help reduce fuel used. Shopping in this manner saves on the cost of transportation and you save money on groceries as well.
Take advantage of the "leaders" that your local grocery store is willing to take a loss on. Their loss is your gain, but don't feel bad about it. If it didn't make economic sense for them, they wouldn't make the offer.
Just make certain that what you're buying is what you really need or what you really want. Buying something because it's on sale is a waste of money unless you can really use it.
Done with Loss Leader, back to Frugal Shopping