There's an obvious problem with cost per unit tricks like this. You have to be able to front the money to buy the big bag of rice. If your food budget is $40/wk, how are you going to spend $88 on a bag of rice? With your non-existent savings account? By eating plain rice and literally nothing else for > two weeks?
Incidentally, the median US household is said by the BLS to be capable of saving $1k/mo after all ordinary expenses. For those who actually save, a savings account typically isn't the mechanism to do it. This leads to "funny" statistics pushed by news outlets on how a huge percentage of people, even HNers who have thousands or even millions saved up in mostly liquid assets, have no savings, because they're sampling either non-existent or non-useful-and-thus-empty savings accounts.
A credit card + bank account
A stable address and room to store bulk stuff
A place to get packages where they won't be stolen
$88
Whenever someone says “the poor can do this” someone comes along to give an example of poor people who can’t. We get it, but there are plenty of poor who can do those things.
The answer is that they can’t get those same discounts buying larger scale items.
I agree there are still some cases where people may spend irresponsibly, but it’s a different problem than “cheaper calories exist in large enough quantities”