Oh come on, Ikea allows you to go directly to the warehouse, use a computer to locate the thing you're after and get lost. It also has maps and shortcuts to get you directly to the department you're after. Costco, on the other hand...
Ikea's showroom has a deliberately serpentine layout. There are direct routes from A to B, but those routes are through hidden doorways. Some of those doorways are marked on the store plan, but they're not clearly signposted. There are navigational markings on the floor, but they only denote one route through - the route that Ikea want you to take.
I still thinks it’s setup for efficiency purposes, or at least their perceived efficiency, rather than psychological queues towards the customer.
Even the stuff when you walk in is based on the monthly rebates.