These huge corporations then expand their control of the market by eliminating small businesses. As these businesses go under, the variety of products available decreases to only the ones manufactured by the large corfporations. The quality of the products will drop as there is no small businesses to compete with. And of course, there will be fewer jobs. We will have a virtual monopoly of power-boxes that suddenly have the freedom to raise their prices.
Savings is by definition relative.
If you shop at Costco then you save money as opposed to shopping at Safeway. But once the Safeways are gone, so are the savings. What we have then is a single type of store, made popular by is low prices, that has eliminated the elements of the market that give it incentive to keep prices low.