Have you ever had the experience of going to Wal-Mart for something, only to find out they don't carry it, or are out of stock? You make 2 or 3 more stops before you get to Walgreens and finally make your purchase. You might have saved 30 cents if Wal-Mart had the product, but as it turned out you spent $2 in gas and 30 minutes trying to save 30 cents
If Walmart's buyers can't browbeat the vendors and manufacturers into lowering the wholesale cost of their products a certain percentage each year, year after year, they just simply stop carrying the product.
Ever try to buy a battery at Walmart?
All they have are crappy RAY-O-VAC.
I can't count how many times my wife has gone there for pantry, bathroom, laundry, and cleaning staples, only to find they've stopped carrying them.