Despite both Sydney and Melbourne recently being ranked in the top 10 most expensive cities in the world to live, Sydney workers are now earning 0.1 per cent below the national average of $69,990 a year, while those in Melbourne earn about 1.2 per cent less.espite both Sydney and Melbourne recently being ranked in the top 10 most expensive cities in the world to live, Sydney workers are now earning 0.1 per cent below the national average of $69,990 a year, while those in Melbourne earn about 1.2 per cent less.