It goes far deeper than that. Many, if not most of the brands you see on the shelves are in whole or in part owned by the same corporation that owns either the supermarket chain, or the parent company.

In fact, several chains are often operated by a single holding group of directly associated companies.

There is usually a high end chain, a middle market chain, and a discount chain, all of which are selling mostly the same products, but at different prices. The discount chains are substantially cheaper. The group targets the rich, the middle class, and the poor, with the goal of servicing all available customers in a target region. Rich stores are overpriced on purpose. Like Apple computers. You know you are special because you do your shopping there.

In terms of supermarket competition, it does exist, but at the conglomerate vrs conglomerate level. There are only a few competitors. It's just like Coke and Pepsi, two large groups that dominate almost the entire market, each with their own full line of beverages. Most retail outlets carry either the Coke line of products, or the Pepsi line of products, but less often both in the same building. Coke and Pepsi bid against each other for retail space via discounts to the retailers.

Here's a pro tip - house brands. Examine them closely, because they are usually the identical product as the brand name, produced on the same assembly line, in the same factory, with only the label changed. The supermarket chain doesn't always buy the manufacturer, they have enough purchasing power to get the deal they want anyway.

Then there's coupons - but that is a whole other discussion:)

If you want to save a fortune, you use coupons, and buy many of your products at the discount store. Doing this can often save you 50% to 75% on your grocery budget. It really adds up over time. Do you know of many other investments that return a regular return of 50% to 75%? No, you do not.