The long answer is that most supermarkets do a very good job of minimizing this waste. Almost all departments, especially ones with perishable items, order to sell out and should come very close to running out before their next order arrives. Think about that the next time your supermarket is out of fresh wild salmon. Would they really bring in one extra twenty pound case just to sell you an eight ounce fillet at 8PM the night before fresh fish arrives? Depends on the market and how aggressively the store wants to capture sales, but mostly, no.