The justification for building the stadium (largely at public expense) is that it forms part of the New York Olympic bid, but actually it is for the New York Jets, too. Since no-one in New York thinks the city has much chance of picking up the necessary IOC votes, given recent military events, the need for the stadium begins to look dubious. Moreover, it would only be used by the Jets for football games 12 times a year, when most of the spectators are corporate types who are about as likely to use public transport as Margaret Thatcher, so no-one believes there will not be new traffic congestion in the area. There are other parts of NY that could accommodate a stadium and parking without difficulty, but there is another issue at play: conventions. NY rates nowhere in this lucrative market, not having the appropriate facilities. The real estate promoters of the scheme are obviously pushing this as a reason for development - without mentioning the traffic implications.
The stadium would sit atop the Amtrak rail area where trains are stored, which would mean a $300 million deck being built as part of the stadium. New Yorkers think this must make the idea the most expensive stadium in the world, but they have not looked at the figures on Wembley where the current anticipated cost is £757 million.