Salary for an experienced engineer (employed) is $80k.
Salary for a consultant (employed) is $80k. This consultant is hired out to a company that wants his services for $230k usd per year, but the company can now terminate this contract at will.
The consulting company has to pay the employee's salary regardless of whether they have a contract or not. The consulting company sets aside a portion of the $150k/year/employee profit to pay their employees if it's hard to get a new contract, but of course they will lay off their surplus workforce if there is ever an economic crisis. It' a super profitable business when talent is in demand. If demand is unusually high, the consulting companies compete to provide slightly higher salaries, so they do push the median wages up. So at least that's good.
The consulting companies love hiring new grads, because then they get away with paying a $50k salary, but earn the same profit. The clients can't tell the difference!
If you're smart, senior and well-connected, you'll get your own consulting contracts without the middleman, and make $230k/year directly. You do take some more risk; if the market tanks, you'll be laid off immediately instead of with 3-12 months notice. You'll also be the first to go.
As a freelancer, it can be hard to get contracts with the best clients, because they don't want to spend effort hiring recruiters that recognize talent, and hence pick exclusively from the top 10 consulting companies.
So to answer your question: If this setup looks suspiciously like a shady wage fixing scheme, it's because countries with a predomimantly Protestant work ethic like Norway and Canada don't think that's such a big deal. People were born equal, they're supposed to make equal money. (Company owners notwithstanding, now as during the Industrial Revolution). Market efficiencies don't factor into it at all, and you're a right-wing conservative if you suggest otherwise.
I am not joking.