Perth is not that expensive if you're prepared to put up with a 40 minute commute (O horrors).
The town I grew up in, Darwin, is now regularly amongst the most expensive capitals in the world for rent. And food, petrol etc is a helluva lot more expensive there than it is here in Perth.
Getting investment in Perth is tricky though. Investors in Perth understand the mining lifecycle. If you see something interesting on a map, you can round up some geologists and drillers and raise $10 million in a few weeks. It's basically the Silicon Valley of mining.
But god help you if you want to launch a software business. There's one venture fund and so far they've invested in one (1) software venture -- and that was Filter Squad, after Discovr was successful.
All the Australian action is happening over east. And there's nothing much there either.
If I could up stumps, right now, and move to the US, I would.