>>So, I will ask you again: how much money does someone have to earn to be considered a "high earner" and who decides what the threshold should be
It actually doesn't matter as long as the burden falls equally. Whether you pay $30% tax or 60% tax over a certain threshold, your status in relation to the Jones remains the same if they're paying the same. The distortions and resentments begin if the Jones only pay 18% tax because of some loophole and after a decade they're now well ahead and are pulling up the ladder after themselves.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
