There's a reason why Costco's layout changes constantly — and it's not just to trick you into buying more stuff

• Costco is known for its "treasure hunt" shopping experience.
• This means that products are shifted around the warehouse before opening every day. 
• While some say it's a merchandise strategy, others say it's what makes going to Costco so "fun."

When you visit Costco, one thing is certain: you never know what you'll find or where you'll find it.

This is what's known as Costco's "treasure hunt." The design layout of every warehouse is constantly changing as employees shift products around and rotate the items on sale.

For some, Costco's treasure hunt is an infuriating merchandising strategy that ensures shoppers spend more time in the store viewing products they likely wouldn't have considered buying if the layout was more straightforward.

But David and Susan Schwartz — two of Costco's biggest fans and the authors of "The Joy of Costco: A Treasure Hunt from A to Z" — say that's a complete misunderstanding.

Before publishing their book in September, David and Susan spent seven years visiting over 200 Costco locations around the world to learn more about the store. During that time, they were able to go behind the scenes at some locations to get a better sense of how the company functions daily.

"One of the most exciting was in Sterling, Virginia, where they let us go see them become showtime ready," Susan told Business Insider. "Showtime ready" is a phrase used by employees at Costco to refer to preparing and organizing the warehouse before opening.

At 4:30 a.m., the couple watched as Costco employees used forklifts to reorganize the labyrinth of aisles. According to the couple, this isn't done to confuse or trick shoppers — it's done to entertain members with a shopping experience that is always new and exciting.

"They always want to keep it interesting when you come into the warehouse," Susan said.

"People say, really obnoxiously, it's to trick you into buying stuff. It's not. It's just to keep it interesting and fun," she added.

"It feels random, but it's actually not. They think about it pretty carefully," David said.

The couple's opinions are backed up by Costco employees, who previously told BI's Áine Cain that they never purposefully hide products to trick customers.

"We just don't have the room to play these kinds of games," one employee said.