A rule of train travel, too often overlooked, is that successive Amtrak departures to the same destination are often priced differently. By failing to inquire about the price of earlier or later trains, one often gives up a great deal of money.
I learned that lesson on a recent trip from New York City to Philadelphia. Learning that a particular train left at 10:52 am, I failed to ask about the trains leaving slightly earlier or later. As a result, I paid $75 for the one-way ticket when I could have paid only $40 for a train leaving 20 minutes later. The train I took was an express making only two stops on the way to Philadelphia, whereas the cheaper train was a local making four stops en route. For the insignificant advantage of arriving a few minutes earlier, my wife and I paid $70 more than we could have.
Tickets on Amtrak trains leaving at different times of the day are often priced differently. Apart from the time difference, some Amtrak trains are express in nature (I am talking about normal, regional trains, not the ultra-fast Acela), while others are locals making several stops. A simple inquiry to an Amtrak ticket seller (or a search on Amtrak's website) will often reveal the opportunity for major savings.
On the return trip from Philadelphia to New York, a helpful Amtrak employee pointed out that if we only left 18 minutes later than we had planned, my wife and I could save $70. We followed his advice and enjoyed a trip that differed in only a minor way from the express train we had planned to use.
So ask when you purchase a ticket in person or on the phone. Are there alternatives? Earlier or later trains? Locals or expresses? Departures at less popular times? The inquisitive traveler saves a great deal by making a few inquiries of the agent at the Amtrak ticket window.