I went when visiting my bro in canberra. Only bought 3 things and spent $100! LOL. It adds up very easily.

Dishwasher tablets. Two boxes for $30... they're normally $28 each! Washing powder I got 10kg for about $30. And I got DH his root beer lol, which was also around $30. Not a bargain, but there's not many places that sell it

My SIL tried the fresh food, but even that seems to be in bulk, so there was waste. She said it would be good if you're having a bbq or party or something.

I didn't really have a good look around as I hadn't really budgeted for a costco shop LOL. Would love to do a real price comparison and see if it's worth it myself. Things like teabags and shampoos etc I'd be interested in.