How long until we get to peak and off-peak rates for data usage by ISPs, much like some electrical utilities?
Luckily, I think competition is going to be making things better for the Australian ISP consumer. That, and recent improvements/additions in undersea cables.
I decided I prefer a limited plan where I know what service level (particularly latency and throughput) I can expect. For instance, plans with Adam and Internode are not that much more than a TPG plan for more usage than I'll forseeably use (I get 500gb a month or so at 20mbps + VOIP for $100), but the difference in gaming latency and actual speeds are both considerably more stable and faster than friends on TPG.
Given that your plan is 60% more than mine, I'll gladly pocket the difference and live with the minor problems I've had. As another poster mentioned, I chose to vote with my wallet. Generally small quotas + absurd off-peak times (where the majority of the quota is allocated) make my blood boil and I'll support anyone who helps break up the status quo.
Then again, I suppose you could argue cost per GB = integral(download speed * time) / cost per month, so 1GB at slow speeds is costing me more in terms of time-bandwidth product at peak rates than otherwise. Soft data caps and peak-time QoS might also be happening behind the scenes, skewing matters more.
Let's say you're an ISP and you have a 10Gbps connection to the outside world, and the routers etc. that can keep up with that speed.
To a first approximation, your costs to serve up 10Gbps to all the customers in your area is 0 (you've got to pay for electricity and engineers and etc, but this doesn't vary with user activity).
If your customers in your area all queued up nicely and downloaded stuff at full rate, never overlapping with each other, you could transfer 10Gbps * 1 month for basically nothing.
However, your customers all want to do stuff at the same time, and thus contend with each other for a slice of that 10Gbps. If you want to serve all of their requests, you're going to have to spring to upgrade your total capacity.
If you don't own your own fiber, you have to rent a link from someone else, or if you do and there's no more available you have to physically come up with more (and pay to dig up the road and etc.). Now your routers and etc. might not be able to keep up with your new backhaul speed, and you have to upgrade those...
You really want to measure "Marginal cost of +x Kbps during the busiest typical hour."
I'd be thrilled if someone tried it, though. It's more honest and more likely to address bad user experiences than arbitrary "bytes transferred per month caps."