Melbourne daily travel is fixed with a myki card. Cost ranges from $4 a weekday for concession or $8 a day for adults over 4 hours. Half that is your trips are less than 2 hours. you get multiple trips. better than Sydney. The best thing is you can even get to the airport but it will involve some changes. I wanted to post this on a query but felt the general advice would benefit others in a separate post.
For airport arrivals, you must have a myki card. not sure if these are available at the arrivals kiosk. If so buy them. they will pay for themselves immediately on your daily trips.
With you myki card which can be topped up as you buy it, set up auto topup as you will run out sooner than you think. From the airport arrivals terminals, walk past the skybus and save $18-19 which my wife paid going to the airport as it would have taken her an extra hour by public transport from where we live [40km from the city]. Wave skybus goodbye and keep walking into the car park at the end of the terminals. The bus interchange is there opposite terminal 4. Keep walking around the S bed until you see a sign for route 901 which will take you to Broadmeadows station. There, take a train where you want to go. e.g. any of the city loop stations from where you can changeover to other suburban routes if needed.
At night skybus cuts out to my suburb after 720pm. Startbus is a good alternative but it only services a smaller range of suburbs near the city. It drops you to your door unlike Skybus.
If you come at night to a far suburb the buses to your local address may not run so you may need a taxi.
e.g. I went to broadmeadows stn from frankston line to craigieburn line and then picked up my wife from the airport and took a 901 back to broadmeadows stn. from there the train runs to flinders station. then took a train back to frankston. unfortunately buses run only till 10pm latest at frankston stn so we had to take a taxi home.
the myki will be good for as many trips as you want. auto-topup is best. I recently moved to Melbourne from Sydney and this tip would have saved me heaps as the next days we walked or stuck to the free tram zone until we realised myki could save us hard cash.
cost with myki is $4 [concession] or $8 [adult] or half that if your trip is less than 2 hrs.
A few years old now but even better (if you have a car) is park around Gladstone Park Shopping Centre for as long as you want and hop on the 901. 5 minute ride to airport.