Something no one's mentioned: when you're eating 4,000 kCal a day or so, there's one thing you must never, ever, ever come close to running out of.
Toilet Paper. It comes in blocks of, like, a billion for 10 bucks. The good kind, too. None of that one-ply shit for me, thank you.
Plus, the pharmacy section is (especially for the generics) is way cheaper when, as opposed to normal people, you eat multi-vitamins, calcium pills, and glucosamime by the handful.
But, the poster above is right about suff just disappearing from the store. A few months ago, I found massive jars of all-natural peanut butter and stocked up, but now my CostCo doesn';t carry it anymore, leaving me to buy tiny, expensive jar at the supermarket every two days. (I put, like, three heaping tablespoons in every shake. Yummy.)