Thinking about pyramids

I was looking at the Shard from my office window. It occurred to me that a tall thin pyramid is a silly shape for a building.

Cuboid volume: length × width × height
Pyramid volume: length × width × height ÷ 3

So the Shard is three times the height it needs to be for its floor space, if only the walls didn't lean inwards.

(OK, not quite, because the top few floors are an empty "spire", but they're small so it doesn't make much difference.)