Mobile in Australia is an oligarchy. Since the collapse of ISPone there seems to be an active effort being put in by the 3 mobile carriers (Telstra, Optus, VHA) to protect their margins and make it as difficult as possible for MVNOs to start up. Prepaid plans should not be that expensive - I have had worse experiences in Germany.
Your home Internet is a different story. The caps exist to support the limited resource. Unlimited has been tried and is always abused. The wholesale access charges within Australia require ISP's set limits or it's the same as everyone leaving their taps running and lights on.
Cloudflare's experience with Australian bandwidth pricing will be related to the costs charged by the tier 1 carriers (Optus, Telstra and AAPT [note: AAPT may have started peering; I am a little out of the game there now]). They will be seeking direct access to eyeballs and being charged for the privilege, much the same as the issues Netflix is facing with eyeball carriers in the USA.
On the cost front, the underlying delivery cost for some of these networks is higher, as they try to keep consistent pricing across all regions of Australia. People in small towns pay the same prices as people in the largest cities. The country is big and the population density is low. Contrast that to Europe, and carriers there have a much easier time making money.
Despite all of this, negotiating peering (paid or otherwise) in Europe with their incumbent carriers is just as difficult and costly as in Australia :) ��- unless you are Cloudflare-size and have hit that critical mass of outbound content that makes you attractive to these incumbents.
Macca