You're going to have to book out farther than that for a fair comparison.
A better comparison would be emergency last minute trips THAT HAVE TO BE DONE RIGHT NOW!
A good example would be suddenly having to go to Florida following the death of a parent/grandparent to put their affairs in order.
A quick look on travel sites and booking systems during 5:20 to 6:00 PM on 14 May 2011 showed:
AMTK #97 Silver Meteor: 7:30 PM (2 hours from departure – WAS/ORL): $225 for coach, $583 in total for a roomette upgrade (17.5~ hrs)
United #260 10:05 PM (4.5 hours from departure – Dulles/Orlando Intl): $1,187 (2~ hrs nonstop)
(Waiting for the next day's flight listings brought the price down to $500-600 if you were willing to put up with a connecting flight to Orlando with a stopover in Atlanta or something)
You can see that the cost of traveling down to FL is less than half that of the airlines -- and you can gain the extra advantage of being able to sleep on your trip, and such a late departure plays to the train's advantage:
Air: Arrive at Dulles at 9 PM, fly out at 10 PM, land in Orlando at about 12 Midnightish; then crash at a hotel you found at around 1:30 AM. Sleep late, get out of bed at maybe 9:30 AM for the day.
Train: Get to Union Station at 6:45 PM, leave at 7:30 PM, sleep in your roomette, and arrive in Orlando around 1 PM.
Essentially with the flight, you're paying twice the money to gain about two-three hours of time if you have to leave IMMEDIATELY that afternoon.