This isn't really right.

GDP per capita is mostly static since a large increase pre-COVID during the explosive China growth years 2005-2020.

Most variations since are exchange rate variations more than actual changes in GPD vs population (GDP is usually denominated in USD)[1],[2]

Low GPD per capita is definitely NOT correlated with high migration, which decreased in the years GPD per population decreased[3]

If anything low migration is inversely correlated with higher GDP over the last 25 years: high immigration is correlated with higher GPD per capita - but I don't think one should draw a causal link here: the cause of GDP growth in AUstralia is generally accepted as increased raw material exports to China, and that has led to higher employment.

[1] https://data.worldbank.org/indicator/NY.GDP.PCAP.CD?location...

[2] https://tradingeconomics.com/australia/gdp-per-capita

[3] https://www.macrotrends.net/global-metrics/countries/aus/aus...