The Swisspass is not a train ticket itself, it is just a card that allows for tickets to be loaded onto them.
The cheapest ticket you can get is a point-to-point monthly pass for 261.- or even a GA (all of switzerland) for 295.-. Both are valid during one month, starting on any date you chose.
In the case you do not already have a swisspass card, you will get one as you buy the abonnement.