This thread has prompted me to do a rough calculation of my daily food costs plus sundries like batteries, etc., for a four-day walk, so I added up all the stuff I'd ordered online such as freeze-dried meals, isotonic drink powder amd energy bars plus supermarket items like dried milk, packet soups and chocolate.
The total worked out as £14 per day for the trip I completed a couple of weeks ago. I wild camped, so costs for this were zero.
How this compares with how much my food costs at home I haven't a clue, ask the wife, I'd guess £14 is slightly more.
As for pubs, there aren't any where I walk (I tell a lie, I did pass one this year where I spent £3.50 on a pint, my excuse being it was very hot weather, but that was a highly unusual exception, and I didn't like having the weight of the coins in change from my banknote afterwards).
Post-walk I stayed on a remarkably cheap camp site at £6 per night (I'm used to paying £14-15 and up to £20), while pub lunch with a pint and pub dinner with a pint came to about £30 a day. Living like that is a luxury for me, I can't afford to drink out or dine out at home except for a rare Wetherspoons visit.
So neither were anything like other peoples' £40-50 a day.
Petrol for the 220 miles journey to my walk, plus driving around during my camp ste days, then returning home, was £75.