The only Amtrak train scheduled to be taken together as part of the weekend events will be Regional #147 from Baltimore to Washington. This departs on Saturday 1/17/15 from Baltimore at 2:43 PM and gets to Washington 3:30 PM. At this time, "Saver" fares are available for $13. This fare is refundable only by e-voucher. The "Value" fare is $17 , which with an AAA discount comes to $15.30 , so the difference is not all that much. I would expect that all of us can go in coach class for a scheduled 47 minute trip. Business Class jumps to $32.
Any other Amtrak trains will be used presumably to get you to and from the Fest, and any activities that might be planned for Friday and/or Monday if enough people want to do a "points run".