that seems horribly inefficient considering wasted time on the way to/from shop and time spent in queue waiting at checkout, so instead of doing this 1-2x a wee

that seems horribly inefficient considering wasted time on the way to/from shop and time spent in queue waiting at checkout, so instead of doing this 1-2x a week you spend like 3 times more time on these fixed items and let's ignore the promotions especially for bigger packages/bulk purchases I don't think it's really doable unless you are single and you have big chain right on the way from work, otherwise small shops in convenient location next to your house will charge you premium compared to big discount chains