Seriously are you all on a different planet to me? There is no mystery here just simple free market economy combined with greed and human nature.
I am a UK trained teacher and get paid at a rate that is similar to that in the UK but with a bunch of other 'incentives'. I know that there are Indian teachers in the other school in the community who get paid far less than I do because they get paid at a similar rate to back in India but again with 'incentives'.
Is that fair? Of course not, welcome to the real world. The gardeners at my community work longer hours than me, in stifling heat and for 6 days a week and get paid a pittance. Why do they do it? Because it is a job and allows them to send money home. Is that fair? No. Are they being exploited? Of course. Once again, welcome to the real world.
I am only here for the money, I hate the society here but I can't change it any more than I can do anything about orphans living off of food scraps in the worlds poorest countries.
People are paid unfairly here because they can be. A more interesting question to me is why people who do 'meaningless' jobs get paid so much more than people like paramedics, nurses, teachers etc. Are footballers or celebrities 'worth' the money they are paid?