I don't think it's really about TP. Any more than $4.99 chickens is about selling chickens. Note that both are in the back of the store, and they move merchandise often to keep shoppers changing their traffic patterns so that they pass more 'impulse' merchandise. It's not a mistake that shoppers at Costco have to walk past jewelry, computers, TVs, appliances, clothes, booze, in order to get to the cheap TP and chickens. Then they conveniently put the food court and auto service out past the cash registers where they don't care if people loiter and spend even more money grazing and shopping for glasses. while their tires are mounted.
It's a formula, BUT IT WORKS!
Jim