Yes, it's blown out on cost, primarily because of tunnelling issues.
Your point about large amounts of storage and the network capacity etc is correct, however, no one "just assume[s] a infinite copper grid". AEMOs ISP includes transmission network upgrades to both connect Renewable Energy Zones (eg offshore and rural REZ in Victoria).
The problems of "baseload" disappearing both because of the age of the generators and the variability of RE because "always on" generation doesn't work well with variable generation has to be solved, but storage is growing now at the same sort of rate as generation, especially co-located solar/storage.
It is exceedingly rare for unexpected weather events lasting several days across the entire NEM. In fact, it has never occurred.
Your point about large amounts of storage and the network capacity etc is correct, however, no one "just assume[s] a infinite copper grid". AEMOs ISP includes transmission network upgrades to both connect Renewable Energy Zones (eg offshore and rural REZ in Victoria).
The problems of "baseload" disappearing both because of the age of the generators and the variability of RE because "always on" generation doesn't work well with variable generation has to be solved, but storage is growing now at the same sort of rate as generation, especially co-located solar/storage.
It is exceedingly rare for unexpected weather events lasting several days across the entire NEM. In fact, it has never occurred.