Depends on the items. Things that you don’t typically buy on a weekly basis is the draw, then while You’re there you may as well get your stuff for the week.
We don’t typically go to Costco every week, for us it’s a once a month type trip. Things like dog food, toilet paper, paper towels, meat that you can freeze for later (typically the best quality meat around here), cheese, treats, etc.
Most things that are expensive elsewhere are cheaper there and in a larger size.