We spend about £100 PW for 5 (2 adults, 3 children 16,12,11)
No idea how you do this unless:
a) you have tiny appetites and rarely snack
b) only buy the essentials
That’s less than £1 per person per meal, including non-food groceries
It's easy doable in our house although we are only 4 adults, 3 male and big eaters and female who loves food!
A big of porridge can last a couple of weeks and only costs about a quid.
Packets of chickpeas, haricot beans, lentils, cous cous, semolina etc are inexpensive and last for ages,same with pasta but can be the base of many meals. I tend to buy frozen peas and mixed bed and frozen chopped onions. Again really cheap and used nearly every meal.
I don't spend money on coffee pods, they are ridiculously expensive, we don't have cereals or things like crisps and biscuits in. We cut all that out about 15 years ago for health reason.
I do like to meal plan and have themes for a week or two. I'm using my middle eastern cook books at the moment and already have things like orange blossom water, Rose water and pomegranate molasses in. I make my own lebnah and flat bread and they cost next to nothing. All My herbs are grown and I have a fantastic on going spice collection.
I do like a drink but had loads in as people bought me different flavoured gins for Christmas, my birthday, Mother's Day, and for thank you gifts so I've not had to buy any. I did inwardly sigh at one point when I got another bottle of Rhubrb and ginger gin but I'm thankful now!
I'm not being preachy or like some Earth mother, just explaining why I haven't noticed an increase in our shopping bill.