I would guess data center cost savings from off peak energy consumption.

Cars?

Smart homes?

A whole City?

The Apple Arcology? Their headquarters is a prototype?

Wouldn’t surprise me, given Musk is hoping to do a Mars colony and Bezos is hoping to do O’Neill cylinders.

I've been waiting for over a decade for IKEA to get in on the action with an IKEArcology!

They already have model apartments with the square footage listed. They just need to establish different SKUs, and then instead of going to the warehouse to get your flat pack, you get a key card for the elevator and go up to your apartment! Though I think if the Swedish Meatballs became my staple diet, and I were exposed to their desert display daily, I'd die an early death.

I've had those books on Space Colonization by TA Heppenheimer, and some of the illustrations inside have a definite IKEA-ish vibe.