You assume that the ROI of oil will be more in the future. If Australia weren't a top materials producer the entire country would be poorer -now-. That oil money doesn't just evaporate, it reverberates through the entire economy and goes into other goods and services, which also grow. That economic growth will be better for the country, tenfold (and that's playing down the impact,) than just sitting on the oil and waiting for the price to go up...which it may never, due to dwindling demand and alternatives becoming cheaper.