Salaries are like house prices, people will always earn what their employer is prepared to pay for their services.
If you complain that they get paid a lot more than you, I suggest you brush up your skills and start ringing round.
People like football (I don't, but I am generalising) and while they are prepared to put ludicrous amounts of money into the game (Sky channel subscriptions, season tickets, shirts etc) then that money will always move towards the value-adders in the organisation, in this case the players.
Yes, I think it is ridiculous that they earn that much, but I can totally understand why it happens at the same time. Should it be spent on something else? Yes, but you have to convince 4 million people to stump up £20 a month to watch it, whatever it is....