the real sunk cost would be the opposite approach: spending 60 blns on boring tunnels through mountains that nothing else connect to. what would be the benefit

the real sunk cost would be the opposite approach: spending 60 blns on boring tunnels through mountains that nothing else connect to. what would be the benefit of tunnel from LA across the mountain range? or a tunnel from SF across the diablo range??? keep in mind these ar elike half of the project cost