"the absolute worst shopping experience I can think of"

Indeed:

* Short opening hours

* checking the membership card at the entrance

* cell phone salesmen inside

* item locations change randomly

* items randomly disappear for weeks at a time, as if Leonid Brezhnev was in charge of restocking

* waiting at the exit for someone to check your receipt

* for a while, they'd check your receipt at the self-checkout and then check it again at the exit

* 1970s level IT, inaccurate inventory information

Microsoft used to give a cash bonus for patents; I imagine Costco has a bonus program for new ideas to make the shopping experience worse. Some ideas:

* throw lit firecrackers into the crowd

* pour oil on the floor so people slip

* complete darkness inside the store

* every 10th person at the checkout has their credit card cut into pieces

It's because they are so busy. Yeah, costco is the one store I go to that people seem to have 0 spatial awareness. Every time I go, someone will just stop moving in the middle of the aisle, creating backups, without any shame. But I bet if your other local grocery stores were as busy as costco, they would have the same issues.

Agreed. The entire store is wired to encourage impulse buying and keep you from making rational decisions about whether you'll be able to finish that 3lb container of guacamole before it goes bad.