I think it might be exemplified by a personal example. I went to one near the end to buy a standard, wooden block, JENGA toy for relatives. They didn't have any in stock other than some crummy cardboard sticks version (absolutely unable to stand up to the abuse a child under 12 will dish out). I think I ended up ordering one from Amazon with Prime or hitting up a Target or something...
As for the 'category killer' thing, that's probably an example of Market Failure (regulation failure). For a fungible commodity product, there probably should be a requirement to provide access to the same price to all players in the market. That might mean that the price at a generic warehouse in one of the major shipping ports is that price. Stores / groups of stores would still need to leverage shipping and distribution networks, but it'd at least give places a _chance_ to compete.