The whole game is rigged. It's programmed to entice spending (don't!) and increases cost when you save up gold coins. In all my time playing, I've never once encountered a human player, all bots. The gameplay initially is fun, but as you increase level you start to encounter bizarre games where every foul by one team goes unpunished and the other is yellow & red carded. Or where a level 50 player which can't get anywhere near a 15.