I'm in the supermarket business and no, we don't pricematch. Profit margins in supermarkets are really low, it's a more cutthroat business than computer parts. Generally a lot of what you see in the ads are loss leaders. They're products that the store might lose money selling to you. You just have some killer deals in the flyer to get customers in assuming that they're going to buy stuff you make money on as well as the sale items. That actually works, but it falls apart if you start price-matching as then you're not only carrying your own loss leaders, but you're covering everyone elses as well. Since Pathmark, Shop-Rite, Stop &Shop, Shaws, etc (adjust chains for your geographic area) all run different ads every week, you wind up with almost your entire store on sale and you're not making any money on anything anyone buys. Hell, that's not only true for sale items, but for regular items as well. There are certain key items that you're forced to sell at a loss every day simply because your competitor across the street is selling them at a loss too and you can't afford to let him beat you on pricing. If one chain decides to be real bastards and start selling bread at 3 loaves for a buck or milk for $1 a gallon, every store in that area will match those prices just to avoid losing business. Add to that the problem that unlike an electronics store where a customer is buying a single item like a TV, in a supermarket a customer might have 100+ items in their carriage and many would pricematch EVERY ONE of them. You'd never be able to get through the registers.
About the only pricematching deal you're going to get is that a store might price-match a competitors in-store coupon.