The writer is too kind to the operators.
The cost of internet peering/transit is negligible in this context - the only significant cost of supporting heavy users is the impact on capacity/performance in the mobile network. Hence the subscriber charging regime is decided by the service provider purely based on their internal costs and their analysis/expectation of subscriber behaviour is response to tariffs.
Given that all the networks have the capability of turning off data services when usage thresholds are reached, their policy of continuing to deliver service, albeit at a much higher charging rate, so high that no rational consumer would continue to use it, is clearly intended to deter subscribers from taking lower price plans, or, in case of 'unlimited' usage plans, simply profiteering.
A simple remedy would be the requirement to explicitly offer subscribers the option of turning off data service when thresholds are reached, or, better still, outlaw punitive charging regimes in favour of either pro-rata charging for excess use, or simply blocking service when thresholds are reached.
Of course, were that principle to be extended to call and text services, it would blow a massive hole below the waterline in the whole current mobile service tariff regime, which depends so heavily on getting subscribers to buy more minutes/texts than they need, simply to avoid punitive charges when usage thresholds are breached.
So don't expect any changes to any tariffs any time soon!