If you buy a roundtrip ticket you must go down on the same train you came up and the train only stops at the summit for about 30 minutes. You could wait longer and try to find a seat on a subsequent train, but seats are not always available. The price for a one-way ticket down was $22 last year. Also, you do not want to park in the Cog RR lot because your parking space is only good until your original train returns. Your could make a reservation on a later train for the ride down, but you would likely have to pay the full roundtrip price.