Yes, the import tax rises every year.
For example, a 2 years ago on an decent R32 gtr it would be around 3k AUD, one of my friends just imported one cause the yen was down earlier this year but the tax had shot up to around 7k to 8k AUD. And a NA1 nsx base type, had tax of 7k AUD last year, this year is 15k AUD.
They base the tax value of recent transactions of that model in the local HK market rather than the condition!
To further worsen the problem, there is not enough affordable parking space. So if you have a few cars, then just parking them somewhere adds up quite a bit.