Groceries are expensive but the margin on groceries, the actual profit per product, is ridiculously low for the retailer. They make up for this low rate of profit, with volume, getting 1 to 3% profit on each cart of groceries is feasible when you’re serving thousands of customers a day.

Costco only has a 2.5% profit margin for example. And that is with lots of store brands, and very shrewd negotiating to get massive volume discounts.