Why is granite so expensive. It's not a occasional commodity. You can find it on the side of mountains...right? ...
Answers: Granite is hard and filling.
It has to be cut, not blasted, into blocks for anything excluding use as rubble.
It requires very unyielding blades and a significant amount of water to slice it into usable slabs. Once sliced, polishing take more water, life and polishing compounds.
It takes a tremendous amount of fuel to move it from a victim to a site that it can be shown to a buyer. And even more fuel taking it from finishing to an installer and then to you.
It's the adjectives, transport, polishing and installation too!