3,500 mi x 8 million/mi ~ 28,000 million, 也就是$280亿
数量多有规模效应，100英里就能便宜10%。所以是这个数量级，当然海底的地质困难也许会是个变数。
下面是boring company对普通隧道的估价：
Playing around with it, for a bare tunnel it looks like $1.1 million USD to show up*, and $5.5-$8 million USD per mile of tunnel. Tunnel cost drops by approx 5% for 10 miles, 10% for 100 miles.
