It's not the actual train trip that is making it expensive. Rather, it is the station access fee that you have to pay for the privilege of using the airport stations as the stations are not owned by Cityrail, but a private company, Airport Link, which I understand is owned by Westpac. The company owns four stations: Green Square, Mascot and the two airport stations. The NSW government pays the access fee for Green Square and Mascot, but does not for the other two. Without the station access fee, it would cost about $4.20 from the airport to the CBD. In comparison with airport services in other cities, it is not that expensive. However, do they have dedicated airport trains as you just get a regular Cityrail service in Sydney. It's OK if you don't have much luggage during peak hour, but it could be a tight squeeze otherwise. For locals, the 400 bus route is OK if you're travelling anywhere between Bondi, airport, Rockdale, Campsie and Burwood.