The twin-track tunnels under the Hudson used as New York City to Washington trains start their journey have been in place since the early 20th century, replacing ferryboats from a Pennsylvania Railway terminal on the New Jersey side. Since then there have been progressively more commuter services added to the route because there were several other former companies, all of whom also used ferryboats from their own separate terminals, which have progressively had their services moved onto the route.
I think I am right that there have been no new crossings of the Hudson into Manhattan, road, rail or subway, built since the 1950s, and with the end of the ferries there is actually less capacity.
The USD 20bn cost of an additional two tunnels seems an extraordinary cost for what looks a straightforward tunnelling project with some 4-tracking on the NJ side,