I am lucky enough that I can choose what I buy for the most part primarily if I like it without thinking too much about whether or not a less expensive option exists. I do try to watch what I spend, but the difference of a few cents is not going to make me abandon my 6-in-1 Ground Tomatoes in favor of store brand crushed.
How does this relate to having a master list, you ask? For the first time ever, I had to pay for my own Costco membership. I have been thinking about the reasons that I shop at Costco. There are only two of us, and we have nearly zero storage space, so it is not the bulk shopping for sure. So what is it? I'll tell you. It's Rader's 3 Berry Blend, Ling Ling's Pork Potstickers, Kirkland Brand Olive Oil, and the meat which is in small enough bulk that I can actually store it in my freezer.
Funny enough, these are the first 4 (ok 6, since meat is actually ground beef, pork chops, and boneless-skinless chicken breasts) items on my Costco Master List.
The idea behind keeping Master Shopping Lists, is knowing what you buy, and where - and then when you go through your pantry before a shopping trip you do an inventory. This lets you know what you are out of and what you are low enough on that you will run out before the next shopping trip. So you can put all these items on your shopping list. That way you aren't sitting there in Costco trying to conjure up an image of the top shelf of your pantry to see if you have another container of cashews in there. Or you don't buy another box of crackers because you are sure that the last ones were eaten, only to get home to find that was not the case at all. Or you don't get stuck with the not as good potstickers because you forgot to buy Ling Ling's when you were at Costco.
Beyond single store master listing, there is the Supreme Master of Lists. This list covers everything. Every single thing you buy with any kind of regularity. I am making one of these using Excel so I can do some filtering and custom list making. If I can figure out how to host files, I'll post it. In the meantime, you will have to trust me that it is very exciting.