> That is what's frustrating about negotiating for commodities like food.

While I generally agree with you, if you're buying fresh food at a market, such as the apples in your example, it isn't necessarily a commodity. Quality and size will vary from one item to the next; why must they all be the same price? Places where goods tend to be more standardized seem to rely less on haggling and more on sorting: you don't haggle over the price of an apple out of a mixed lot, you pay a set price for a certain grade of apple which has been separated out in advance.