This excuse is being given for a long time and now people assume it to be true. The metro is possible even beneath the sea. Please check what was the original cost of the elevated Versova-Andheri-Ghatkopar and what was the final amount spent on it. Also, when land acquisition causes decades of delay in the projects, thereby increasing the cost exponentially, it is a better idea to start underground metro project and finish it in the original timeline.