Insane but not batshit insane. 1) Shenzhen went from fishing village to a ~15 million population city in around 30 years. So there's a precedent for building a

Insane but not batshit insane. 1) Shenzhen went from fishing village to a ~15 million population city in around 30 years. So there's a precedent for building a massive city in a relatively short period of time. 2) The Line is expected to house 9 million people. Assuming 2 people per house and given the $500 billion cost-estimate, it comes out at $110,000 per house. I've seen brand new apartments in Istanbul going for around that price and that's probably way above the actual construction cost (e.g. it includes land cost, developer's profit, etc.). Remember that the land here is free and there will probably be massive economies of scale due to the massiveness of the project.