I have to agree with A and C.
It is very simply supply and demand.
Why begrudge a builder getting paid that if that is what their employer is agreeing to pay. I am sure Laing O'Rourke are not being purely benevolent!
The best rate of salary increase I have had in the UK was the late '80s when there was a shortage of pilots.
If people are so dissatisfied with what their airline is paying why do they stay? Shortage of jobs perhaps?
It is a free market.