Amazon 1-Click Buy Free Apps

// ==UserScript==
// @name        Amazon 1-Click Buy Free Apps
// @namespace   https://www.ozbargain.com.au/user/49047
// @description Automatically purchase any free apps you open links to
// @match       *://www.amazon.com/*
// @match       *://www.amazon.com.au/*
// @match       *://www.amazon.co.uk/*
// @require     http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js
// @version     1
// @grant       none
// ==/UserScript==

$(document).ready(function() {
  var price = $('#actualPriceValue').text().trim();
  if (price === '$0.00' || price === 'FREE')
    $('#mas-buy-button').click();
});