the actual cost of a trip between times square and the national mall is about $200 all things considered based on the ~0.80 federal mileage reimbursement rate for 250 miles. that train corridor is overwhelmingly successful as well so the idea that amtrak isn't a good deal is at odds with reality.
That's assuming you don't already have a time-depreciating asset in your possession. Per mile cost is about halved if you drive significantly more than average.
People in and around the acela corridor drive significantly less than the national average.