I remember roaming in Africa over a decade ago. The rates were the local operator rate plus a margin - I think 20 or 25%. Since then the cost of international prices has plummeted while the cost of roaming has gone through the roof.
In country calls are typically priced at the same rate as international calls, and the pricing bears no resemblance to the actual costs incurred. For example, a vodafone user in the US making a local call has to pay £1.35 per minute. That's a markup of well over 1000%. International calls have always faced crazy pricing that is once again totally at odds with the wholesale cost.
It's pretty clear the free market isn't working to solve this problem. Good for the Australian government for forcing the operator's hands.