The biggest sleeper consists on Superliner trains these days are 2 standard sleepers and transdorm. That means a capacity of about 30-34 roomettes, depending how many are released for sale in the transdorm, 10 bedrooms, 2 family rooms and 2 accessible rooms on each departure at most. Not all trains have that many. The biggest Viewliner consists are 3 sleepers. They apparently only sell 10 of the 12 roomettes in each car, so that means 30 roomettes, 6 bedrooms and 3 accessible rooms. Again, not all trains have that many sleepers.
The supply, as you can see, is highly constrained. It really does not take all that much demand to fill it. Rationing a scarce luxury commodity, which a sleeper room is, despite maintenence and service issues we all know about, is done by price in market economies. Amtrak is merely leveraging the advantage control of a scarce supply gives it, as any rationally run organization would do. The intelligence and rationality of Amtrak executive management is often questionable, but here they are making perfectly rational pricing decisions.
Many here argue sleepers are a poor value proposition, that First Class airfares and cruise cabins are often cheaper. I agree that sleepers at best are a poor value proposition, even at lower buckets. At high buckets they are a downright
terrible value proposition. However, value proposition is not what determines pricing decisions, supply and demand does and at that point it is pretty much math. As long as there are enough new riders who want to try out train travel but do not understand what they may be getting themselves into, and enough veteran riders who do but go anyway, to fill that highly limited inventory, pricing will remain high. That will hold until either Amtrak degrades so much it manages to drive off its limited sleeper clientele or increases capacity.
We all can and do make our own purchasing decisions just as Amtrak makes its own pricing decisions. A sleeper room is very much a discretionary "luxury" purchase. No one is entitled to one any more than one is entitled to a lie-flat First Class airline seat. For myself, I won't purchase in higher buckets (or get bedrooms). That is where tools such as railsforless.us and
@niemi24s' invaluable bucket charts come in, as well as observing yield management pricing patterns for trains I ride most frequently. Those tools help enable me to ride at a price I am willing to tolerate, which in no way should be conflated with "cheap".
Bottom line, we are observing an iron law of economics in action. You can mourn it all you like, but you cannot change it any more than King Canute could hold back the tide.