Submarines - why?

The SMH have estimated the total spending on our new subs to be $150bn, what purpose do they serve?

http://www.smh.com.au/federal-polit...st-taxpayers-150-billion-20160224-gn32kg.html

Defence? Against?
China would treat conventional subs with no on-board nukes as a speed-bump.
Indonesia? Weight of number in small boats would negate ant sub-based defence.

Offence? Against?
Any offensive action would be part of ANZUS and the US have far better subs, and lots more of them.

Regional assistance? Cyclone in Fiji? Quick, send a sub over for humanitarian aid?

The Collins class were an expensive joke and the only thing that can be said for them is that none of them sank (although Farncomb came close).

Aside from propping up SA electorates, can somebody make a case for $150bn on subs?