If you didn’t have that guy working in Australia, your economy either would’ve shrunk by more than 1000 AUD or you would’ve imported goods or services costing a lot more than 1000 AUD. That guy’s employer pays him 1000 AUD because it is profitable compared to the alternatives.
If you had locals capable of doing the same work, that employer or the government wouldn’t have sponsored a foreign worker. They would’ve employed a local instead.