Maybe, but lawyers, accountants and consultants make millions through billable hours. A relative makes $500K per year on billable hours. I can't knock that. However, in the trades, piece-work is certainly better for the highly productive people.
Billable hours might sound lucrative but remember that that is the top line not the bottom line, and it has to support the whole operation.
If you can bill 1800 hours a year that means you are billing 16800 hours /46 weeks (six weeks off i.e a month's vacation plus stat holidays)
46 times 5 days gives you 230 billable days
1800/230= 7.8 billable hours a day. That is a 10-13 hour day in the office (if you are super efficient ) Basically from when you leave for work until you start to bill depends on your commute.
In your example your relative is likely billing a million a year to have a taxable income of 500K after expenses.
If it takes you an hour from when you walk out the door at home till you start your meter at work in 1 hour you are now looking at adding 2 more hours on non production a day
When you bill time there is no overtime you just bill at your regular rate. Some clients will want a fixed cost for a project and that always cuts your billable hours charged versus the hours you worked on the file.
The financial leverage occurs on billable hours happens you have other staff who also bill their time on a file and their annual billings are greater than their total compensation.
Some of my pals bill over 2,000 hours in a year and bill out at 1200-1500 hour. Many are on marriage #2 and are all working on dying early .