The reason smaller stuff is slightly more expensive is shipping costs. Compare two identical products in any store, the larger one will be cheaper, the smaller one will be more expensive, and this scales with weight.
TLDR: people who have never worked in retail, don't understand retail.
Also, saying that these stores are more expensive is crazy if you actually lived at a time when these stores didn't exist. These stores grew because production moved offshore for many products, and retailers took all that profit to their bottom-line (and the five layers of distributors). A lot of these chains cut this out and returned that profit to the consumer. Ofc, the product composition of each store is different (the ones with more FMCG do more optimisation of store size, range of products)...but yes, it turns out people will complain about lower prices...loudly (I have seen this in almost every country where similar formats exist, the loudness of the people complaining about low prices outweighs everything else).
TLDR: people who have never worked in retail, don't understand retail.
Also, saying that these stores are more expensive is crazy if you actually lived at a time when these stores didn't exist. These stores grew because production moved offshore for many products, and retailers took all that profit to their bottom-line (and the five layers of distributors). A lot of these chains cut this out and returned that profit to the consumer. Ofc, the product composition of each store is different (the ones with more FMCG do more optimisation of store size, range of products)...but yes, it turns out people will complain about lower prices...loudly (I have seen this in almost every country where similar formats exist, the loudness of the people complaining about low prices outweighs everything else).