Some of the wealthiest people I have met are trade business...

Some of the wealthiest people I have met are trade business owners (plumbing, electrical, building etc), with say half a dozen tradie employees that they outsource for different jobs. Some of them would be up there with top bankers/lawyers in terms of income, I'd guess. Probably wouldn't beat a specialist medico though - that's a hard figure to beat!

I know that a lot of the high paying professions make sure that they price-fix and limit the number of new graduates to ensure everyone makes a high income, whatever the broader market tries to dictate. So it's not really a supply-demand equation that is in play. In general the more specialized your skills, the more you get paid. Are tradies specialized enough to make that sort of money? They're certainly specialized, but no more so than a nurse. ...IMO