Hello Tmidovschi,
A one way ticket from Zürich Airport to Estavayer-le-Lac cost 70.- CHF without reduction.
With an Half Fare Card, the ticket cost 35.- CHF.
If you have buy your tickets in a SBB counter, you have to go back at a ticket office, with all your receipts, to do the refund.
I wish you a nice day.
Greetings,
CharlineB