Okay, so I was at Walmart the other day doing a quick grocery trip. I go there for things that I don't have coupons for or don't see on sale at my other stores. I also go there when I don't feel like planning it all out as they generally have good prices overall (meaning not per item, but per shopping basket).
Well, I saw on an end cap (the end of the aisle) 4 packs of name brand canned vegetables for $3.00 or 75 cents a can. I thought that was a pretty good deal, so I put one of each in my cart. But, I always check store brand for peas and corn because I think they are fine (I DON'T BUY STORE BRAND GREEN BEANS - YUCK!). As I went to check the store brand, I figured I should just see what 1 can of name brand veggies was. They were 60 cents a can (15 cents less than the bundled pack per can). Needless to say, I put the 4 packs back and got 4 cans of each individually.
This is why they put stuff on end caps. They know that if you took the time to check, you would see that the same thing packaged differently was cheaper. Plus, you bought 4 of them for 15 more a can than maybe 1 or 2 at the cheaper price. You must keep your eyes open and think about things before you just buy it.
Now I know that 15 cents a can doesn't seem like a big deal, but that is 25% more per can. If you paid 25% more for everything you bought, your $400 grocery budget would be over by $100 each month. Just something to think about. :)