Why is fiat currency worth anything? All it is is a bit of paper? I'd rather have bitcoins than USD where politicians and bankers are destroying the currency.
There will only ever be 21 Bitcoins. ATM there are around 6 million bitcoins in existence so the value of all bitcoins in existence is only around 50 million despite them trading at 8USD each, in the scheme of things they are very scarce. If everyone in Australia wanted a bitcoin right now there would only be enough for ~.25 each.
If you think of how many countless billion there are floating around the world not much needs to go into bitcoin for the price to continue to rise.