The NY Subway has an average speed of 17 mph but Boring Company will have speeds of 155 mph. Boring Company will have nine times the speed of the NY subway.
Musk has said a Boring Company an early 18-mile high-speed tunnel would cost ~$1 billion to build. Later tunnels will get cheaper and approach the cost of adding one lane of road at less than $10 million per mile. The Boring company cost could be completely offset with lower cost bricks made from the tunnel dirt.