The short answer to that is no. Taking my boys grocery shopping when they were kids and asking them to do quick calculations on how much per kilo items work out to be proved that. These days over here in Au they pretty much put a unit price on each product tag.
Buying the big 2kg bag of rice isn’t always cheaper it can quite often be exactly the same price to buy 2x 1kg bags.
Another thing to consider is if you’re buying in bulk will you be able to consume it all within the best by date (which is variable) or use by date (which is more finite) it can be a false economy to by a lot and end up throwing most of it away.
In the end we each have to consider how close we are to shops, how many people we need to feed and storage. I have shops within a 30 minute walk or 6 minute drive. I have those things I need to buy weekly, monthly and way less often just like everyone else.
Queensland has recently got a Costco store but that for us would be a yearly fee + 1hr drive away + bridge toll (and back again) so if you join a store like this it all has to be taken into account. I’ve found over the years that if you shop specials you can usually come up with some pretty cheap prices.