If Amtrak's consistently getting 100% LF's, then they can and should raise fares.
On sold out trains many of the seats and sleepers are already being sold at high bucket. Raise the price even higher for a trip in the same tired worn out sleepers and you risk losing passenger traffic. If the prices go up any higher we will take to the road. I believe that lots of passengers also feel this way. When Amtrak made the 25% discount on the NE corridor permanent, ridership soared to new record highs. It became a better buy then flying. The consumer realized it and flocked to the rails.
Also consider than on LD trains, Amtrak sleeper prices are 3 to 5x what a plane ticket costs and 5-15x slower. Its still twice as high as a first class airfare seat.
What makes you believe that Amtrak has such a great service that they can get unlimited prices? Prices need to be balanced so that tickets can be sold year round. Only a few trains in the non-vacation months consistently sell out so the forumula of supply and demand already applies.
Did you know that the high bucket ONE WAY fare on the LSL from NYC to CHI is $165 and add on for a sleeper is $463 roomette and $863 bedroom. Do the math and you've got a trip that costs $630- $1028 & again ONE WAY FARE. Round trip costs you $1260-$2056. Thats just not expensive, that's highway robbery!