My bet: it's all about the lithium. The Gigafactory (located near a large domestic lithium cache) will soon consume a large fraction of the world's lithium output, and currently, Tesla is completely dependent on other companies to mine it.

My question: will the debris Musk will need to transport away from the next "beta-test" city happen to contain large quantities of lithium? Or will his current suppliers have a new source of (too-good-to-refuse) industrial machinery?