I dont think there is really any "wheeling and dealing" prices with sleepers. The charges for all rail fares and sleepers are listed in a book called a tariff. These are set prices by Amtrak on which all charges are based. Personelly, I won't travel overnight without a sleeper, I had a couple bad trips years ago riding coach overnight, so I won't board with out a sleeper ticket, and never bought a ticket on the Rail Sale or E-bay. If a sleeper is that importent to you, you may want to consider buying a traditional ticket that will let you purchase an upgrade on the spot. Also most Conductors don't like playing the role of Ticket Agent, so they are most likely not going to go out of there way to try to save you any money for a sleeper even if they can.