As a hobby, time is what we invest in a project, and material m(If we don’t think it good enough, we bin it and make another, where possible)
In industry, if the object is to make and set 5,000 injection pumps, and 20,000 injectors, that work satisfactorily, every day. The machines are specialised, automated, and integrated into a transfer line
But the cost is HUGE and amortised across the millions produced each year.
On a hobby workshop, if the time were charged at industrial rates, where the machines are general purpose, (Not industrial quality and not driven to their limits all day and every day) we would be horrified at the cost of one component.
Most of us cut metal for pleasure, not profit!
Howard