Also, you can travel through much of the NEC on commuter rail, which might take a bit longer but is certainly cheaper. I think of Amtrak as the premium rail service, and the commuters as the budget rail service. Sometimes you're willing to pay for the premium, other times the budget service is fine.

Actually, if you figure Acela and "regular" trains, it's really 3 levels of service. And since the commuters stop at more places, sometimes the budget service is a better option anyway depending on where you are ultimately headed.