When GP said business owners I assume they included independent plumbers. I can call the local plumbing franchise and I will pay $150/hr, but the person who shows up at my door is not making anywhere near that.
My friend works for a home security company. They bill $150/hr for labor and he makes $26/hr.
Compared to other countries, Australia is an outlier for tradesmen income, by far. The closest comparison I can think of is software engineer income in the US vs everywhere else.
Working in a trade in Australia is lucrative AF, if you're looking for a way to be relatively wealthy only a couple of years out of high school, apprentice as a shipwright, elevator technician or HVAC technician.
My friend works for a home security company. They bill $150/hr for labor and he makes $26/hr.