Addendum to above: Nobody ever wants to say exactly "how much" money, and that's because every trip is different. Each trip has to be custom-planned around the requirements of the charterer, and there are too many variables to put out a table of charter costs. For example, if there are enough PVs on a train Amtrak will require an extra locomotive...more $$$.
With that said, last year I contacted a PV owner here in the Houston area and asked if he could give a general, "ballpark" figure for a charter which is done frequently: A long weekend in New Orleans, leaving Houston on a Friday at lunchtime serving brunch upon boarding and dinner en route; staying over at the station in New Orleans for three nights using the cars as a hotel with continental breakfast or brunch each morning (lunch and dinner on your own in New Orleans), departure Monday morning with a full breakfast, lunch and dinner before arrival back in Houston. He replied that he could do such a trip for eight adults (four couples) in a sleeping car and dome-lounge car for a total of $20,500.00 including car rental, Amtrak and parking charges, crew (one chef and two stewards), and suitable food and beverage (premium quality, but nothing exotic such as Kobe beef or Beluga caviar). Since this trip uses cars based in Houston and requires no positioning moves, it can be regarded as the "low end" of PV charters. There really is no high end; if you have a million to spend and want to spend it criss-crossing the United States for six weeks in a private train with 20 or 30 of your best friends we can blow through every dime of that million and then some!