Right so it seems somewhat similar to the profits you can make programming. Doesn't seem like a crazy get rich quick scheme, just years of hard work paying off.
Pretty much. There's probably also an "in crowd" aspect to it as well. Everyone I know makes $100k+ as a dev here at least after a few years, but I've had Uber rides with older Indian dev drivers complaining that they can't find a job. I imagine anyone lumped into the whole "dodgy lebo/bogan/asian tradies" stereotype might struggle in a similar way.
Then you work for someone else and probably make $80k or $90k, then you start your own business.
In terms of supply/demand Australians are extremely house proud and spend an insane amount of money on renovations, upgrades, etc, so all the trades are always slammed. Have been for 20 years.