I still have this now!
Of course I was never poor for any real hardcore definition of the word, Third World-style, but I spent a good few years totally flat broke. Money coming in only occasionally covering the rent, utility payments never paid as I couldn't justify spending that much money when I couldn't afford to eat, living off dry bread and instant mash etc etc. It was an experience for sure, and one I never, ever want to repeat! It's only relatively recently that I've stopped dreading the arriving of mail or jumping when there's a knock at the door, or even keeping the curtains closed so no one can see I'm in.
But yeah, I still buy the cheap brands if they are there out of habit. I'll walk down the road to save 10p on a bottle of milk and so on.