Most of a food's cost isn't even the product your buying. Millions of dollars in advertising and eye catching packaging drives up the price of food more than anything else. Despite the increased expense, Americans still tend to buy brand name goods over generics. I just shake my head when someone buys a box of Duncan-Hines brownie mix when the good old generic looking "Great Value" brand is less than half the cost. The extensive advertising is effective and people tend to relate to a certain product or "trust it more." If you wonder if one is better quality, check the ingredients and you'll see that most are the same thing! If you need to trim your grocery budget, this is the single best way to do so.
Now, I'll admit that some name brand stuff is different (Great Value toilet paper is definitely no good) but on most items, generics offer a quick, easy, and drastic cost reducing option.