There is no 'law' of supply and demand. It is a construct. A rational construct that explains a set of behaviours.
It is particularly useful construct, but it is not a law. It does not rule human behaviour, unless we allow it.
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We should restrict supply of aviation training to future pilots
umm.. That sounds a little contradictory to me. But how do you imagine we do that???
Like university with entrance scores? A lottery?
So you want to stop others learning to fly so that a few can be paid more. Sounds a little "elitist" doesn't it?