That only works on goods that have a high margin. Many times a company does that with a product, a competitor will notice and start selling the product at-cost: hence causing their competitor to loose money on the deal. Of course some then take that hit as a loss-leader, but that only works if the products are cheap. That why you'll often see "we guarantee you the lowest price, if you find cheaper elsewhere * excluding apple products * excluding online stores" etc. which I think most consumers notice and end up disregarding the "price guarantee" => however some don't, which I have a hunch might be the most profitable customers anyway....