A few weeks ago my sister Courtney wrote a post about her experience shopping at a retail store, and finding the same item for different prices in different departments. The grocery store can be the same way.
Ethnic sections usually have the some of the same items, like canned beans or spices, as other aisles
Product placement is a huge market for grocery stores with food companies paying for prime spots on shelves, usually right at eye level. Just look down at the shelf next time you're in the store. There often is a healthier and cheaper product than what you see standing up.
Dry beans, lentils, brown rice are often at the bottom of the shelf. Even the garbanzo flour I swore my store didn't have, my sister found towards the bottom of the shelf.
Besides just looking down, look out too. Most of the whole foods are on the outer aisles around the store with the more processed foods being in the center aisles.
The layout of grocery stores is well planned too, with the most popular items being the farthest from the entrance. The bakery department of our store is all the way in the back corner, and the produce section is off to the far side.
I think this goes back to Courtney's theory about the placement of items throughout the store just to try to get us to spend more money. For example, if I need to buy bread for Scott, I have to walk past all the processed food to get it. And it is on the complete opposite from the produce section.
Thinking about other stores I've been in, it seems that they are all like this, with the whole foods being along the outside wall and farthest from the entrance. Maybe that is why it takes us so long at the grocery store, since everything we need is so far apart from each other.