In Melbourne it can be done (MEL to/from CBD) for $3.90 - just takes an hour or so.
Of course you need a Myki.
A timely reminder for Christmas and school holiday/ New Year travellers from serfty that provided one has a little time available - more likely for leisure travellers than those on business - travelling by Metro train to Broadmeadows on the Craigieburn line and then by the 901 SmartBus from outside the Broady station - one minute from the train that has come from Flinders Street - can be almost as quick as roadworks or traffic-delayed, super expensive car parking, Skybuses, Ubers or taxis, especially when the 901 is operating its 15 minute frequency on weekdays until about 2100 hours.
Being public transport, it's a good idea to use
www.ptv.vic.gov.au to plan a trip, remembering to deselect the airport buses at the bottom of the form when one is typing in the journey - otherwise it will automatically direct travellers to Skybus.
It's an even better idea to look at the Metro Craigieburn line and SmartBus route 901 timetables in detail to get an idea of when the next bus or train is if one mode runs late:
https://www.ptv.vic.gov.au/route/view/3
https://www.ptv.vic.gov.au/route/view/7531
The timetables are dynamic, particularly when there are public holidays so one always needs to select the exact date on which travel is to occur. Occasionally there is Metro trackwork (most often on weekends or partial weeknights) so if that is on, avoid use of this alternative as it takes too long.
In reverse, dragging a suitcase down (easy) and up (harder) the ramps at Broadmeadows to get to the platform for trains to Flinders Street is a pain but I and plenty of others have done it.
The Broadmeadows interchange is in an unattractive area but I've never had any trouble, and at night from 1800 hours until the last train there should be two quasi-police roaming around. The bus waiting area is exposed to Pascoe Vale Road traffic but fortunately the office block has a verandah so one generally does not get rained upon - although it can be chilly in winter early in the morning or the evening, with a windy, chilly period being worst.
Users can buy a myki (adults $6) from the blue myki machine in the T2 international arrivals hall, landside, at Melbourne Airport or supposedly from the bus driver. Topping up is also available from the myki machine or again (should be) on board the bus (no change given for latter) with a suggested minimum amount of A$10 making the cost A$16 including the smartcard. From 1 January, a day's travel (zones 1 and 2) becomes A$8.20 which while a five per cent rise on 2016 fares, and therefore way above inflation, is still excellent value compared to what Skybus charges. With this A$8.20 you can transfer between trains, trams and buses all day long within the defined Melbourne metropolitan area, which is spread out.
At Melbourne Airport, the ground floor bus stop location in the car park opposite T4 is not ideal but again it's not all that hard for able bodied passengers to pull a suitcase to or from. It is closest to JQ and TT, then VA, then international flights with the longest walk being to QF's T1.
By using the 901/ Metro train combo and not parking a vehicle at the airport, catching a taxi, Uber or Skybus one can save anything from $30 return (Skybus) to potentially above $100 return (other modes) which is money in one's pocket without major inconvenience, especially if one boards or alights from a Metro train on another line close to one's home or destination.