How would you stay in business if your competitor was offering 20% off your prices because they had better logistics and tracking? Ask consumers to eat the cost due to their latent demand for, uh, inefficient delivery and food spoilage?
But more to the point, there's plenty of grocery stores that ask 20% more than their competitors and are doing just fine; in fact, constant price changes and promotions make it impossible for consumers to really compare if Safeway is cheaper than Whole Foods, so people usually go to the place that's physically closer, has better selection, or better vibes. I can't even know if a 12-pack of Coca-Cola is going to be $6.99 or $9.99 today.