It may sound funny, but if you were only to buy items that are on the bottom two shelves or the top two shelves in the grocery store aisles, you would save quite a bit.
The reason? Brands with either lots of bargaining power or lots of money (or both) provide incentives to the grocery store to place their items at eye-level. The store’s own (and often lower-cost) brand is often placed high or low on the shelves.
Obviously there are some things that this won’t work with. For example, if you’re looking for pure vanilla extract there may only be two options right next to each other. But when looking for cereal, cheeses, or or tortilla chips, you will often find the best deals high or low on the shelf.