If you could describe anyone as Costco experts, it would be David and Susan Schwartz.
The New York City-based couple spent the past seven years trying to visit as many Costco locations as possible to gather information for their first co-written book, "The Joy of Costco: A Treasure Hunt from A to Z."
When they aren't traveling, David and Susan aim to visit their local Costco in Manhattan — which they've dubbed their "happy place" — at least once a week.
"We go to Trader Joe's for some house stuff, but Costco for all the other stuff," Susan said.
Business Insider recently toured Costco with the couple, and they shared the best things currently on sale at the store. Take a look.