Walmart is especially bad about having larger sizes be more expensive than smaller sizes, but almost all of the others have at least some instances of this.
One thing I hate is the incredible shrinking packages and steady prices. So far I've managed to keep within my budget with sales and cheaper meals like beans and rice instead of meat and roasts instead of steaks etc.
I also grow my own produce in the summer, and some in the winter, like spinach, greens and herbs, that helps with the cost too. I mainly started it to avoid pesticides etc.
I managed to get about a year's worth of peanut butter before the price doubled. Bought about 2 years worth of coffee in 2009, that price has now doubled, still have 6 months in stock, and have been picking up a can here and there whenever there is a really good sale.
I cannot remember the last time I bought any grocery items at WalMart. WalMart has lost their way years ago, and then they lost me. And I am not going back.