Australia briefly had something their politicians called a carbon tax, but it was really cap and trade, which is an entirely different system and is rubbish. In particular, you have to give ordinary people back the money the carbon tax collects or they'll rightfully hate it, which cap and trade does not.
And then, because the system they proposed was the miserable one, the opposition leader credibly threatened to repeal it (and then did), so hardly anyone bothered to try to save costs under a program they reasonably expected to quickly go away.
Actual carbon taxes have been implemented in parts of Europe and they do what they're expected to do.
> Fuel for vehicles here, petrol and diesel, has become wildly expensive, but cars have become huge to gigantic.
People used to say "buy a smaller car" as the way to save fuel, since that used to be about the only way to do it. Then carmakers learned you could design an SUV with the use of a wind tunnel instead of shaping it like a brick and then use a smaller displacement engine with a turbo, or a hybrid system, and then you get SUVs with better fuel economy than subcompacts got in the 90s.
Even the huge stonking V8s still get modern aerodynamics and get significantly better mileage than the old ones did.
> To the point where electric vehicle sales here in Australia have fallen off a cliff
Electric vehicles were never popular in Australia. Range is their Achilles heel and Australia is spread out. But then you do a plug-in hybrid that can operate as electric 90% of the time while completely solving the range issue.