Train to/from SYD from city, inner west, east, inner south or lower north shore only ever makes financial sense (costs less than other options) if it is a single person travelling to/from airport at peak time (when traffic is bad) as once you add a second person Uber is cheaper and way less hassle.
People living in outer western/southwest suburbs, Central coast or lower blue mountains may get value if only 2 people, but you have to factor in 1 hour suburban train ride before you can even connect to airport line. Those on northern beaches have a longbus ride to get to station and then still have to change for the airport line. No wonder airport shuttle services are still profitable for those in these areas.
