Airport Link From the International Airport Station, to any of the City Stations, or Kings Cross, a one way ticket is $17.80 AUD
It depends on where you are going to.
A full adult same day return ticket from Sydney Domestic Airport Station to the city circle stations is $34.00 AUD.
As a more general indication, from Sydney Domestic Airport Station to any of the City Stations, or Kings Cross, a single one way ticket is: