In 2016 I bought in 45 kg of new & used prewar parts in from USA as checked luggage. Declared them, as over Au$1000, but no issues and were not inspected or charged duty/GST
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Now you may need to declare for GST (sales tax) and/or import duty, but should get $ back if exported out of Australia.
Make sure they do not have soil or wood attached
May not be relevant, but worth a read
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https://infrastructure.gov.au/vehicl...t_options.aspx
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https://www.homeaffairs.gov.au/busi/...ates-and-taxes
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https://www.wwcf.com.au/customs/