The Department of Treasury appears to be being even more cautious than usual in forecasting the outlook for Australia's key commodity exports, in terms of revenue for the budget.
Treasury is again sticking with its long-standing iron ore forecast of $US55 per tonne by the end of September, despite recently hitting around $US134 per tonne.
But its forecasts for coal are even further away from current levels.
The budget papers released on Tuesday assume the spot price of metallurgical coal will drop from $US512 per tonne to $US130 per tonne by September, while the thermal coal spot price is assumed to decline from $US320 per tonne to US$60 per tonne.
Treasurer Josh Frydenberg gave his long-standing explanation for such conservative forecasts, saying he won't follow Labor and bake into the budget high commodity prices and spend revenue that doesn't end up materialising.
There is also a plus side taking such an approach.
"If these high prices stay here for the next six months that would be an additional $30 billion to the budget bottom line," the treasurer told reporters.
