The price tag for the tunnel is pretty much what you’d expect at the low end of civil engineering costs, so there’s no room in the pricing if things start to go south. Musk’s entire premise is that there are magical inefficiencies in the commercial tunnel boring machines he’s purchased, and he assumes that spacecraft and automotive engineering expertise is sufficiently transferable to uncover those opportunities and redesign a considerably more efficient and cheaper machine. Oh, and using commercial automobiles will be faster, cheaper, and more pax-intensive than light rail solutions. I’m … skeptical. Let’s go with “skeptical” on this one.