Let's stick to nice round numbers and say Apple make something with a list price/RRP/MRP of $100, plus 20% or whatever local VAT/GST or sales tax is, and it costs them $55 to develop and manufacture it. Further, assume that Apple will sell it wholesale to distributors for around $80 or $85.
Apple USA make it for $55, sell it to Apple Australia for $80, who then sell it through shops or direct to customers for $100+tax (ie. customer pays $120). Apple Australia's $20 go on advertising, localisation, tech support, warranty replacements, channel training, retail outlets' slice, etc. US government charges Apple Inc a high rate of corporation tax on $25 profit.
Apple USA sell it to Apple Singapore for $60. Apple Singapore sell it to Apple Australia $80 and costs are as above. US government charges Apple Inc corporation tax on $5 profit. Singapore government charges Apple Singapore neglible tax on $20 profit. Apple keeps cash reserves stashed away in Singapore for a rainy day in case it needs them. If and when it brings the cash back to its shareholders in the USA it will pay corporation tax on the profits then.
How is scenario 2 defrauding Australian government of tax compared to scenario 1, and how is either scenario particularly immoral? Who is being cheated out of what?