The article shows an example of a building where one structural column had to be moved in order to accommodate the hole, and where the hole itself is off-center

The article shows an example of a building where one structural column had to be moved in order to accommodate the hole, and where the hole itself is off-center in order to disturb as few structural elements as possible. Indeed, every building converted in this way will probably need its own bespoke solution (e.g. if the elevator shaft is dead-center, you might cut two smaller holes on either side), but even then it seems like it would be hard for it to be more expensive than starting over from scratch.