We are all on one and the same system, in relation to ADL public transport as for getting to and from the airport, nothing like o, its more expensive because the airport is privately owned, and people going to and from the airport (in SYD (stations), can afford to pay more to get to it and from it-Sydney Airport that is).
ADL is egalitarian, same as PER domestic. ADL and PER public and airport travellers pay the same fare, to and from the airport, as like others in the zone.
Of course, we can't physically top up Opal in ADL, unless you do it online via the Opal website.
If the state govts of Aust's states were on the same ball park, we would have one and the same public transport ticketing system for all states of the nation!