I'm on mission 23 and unless my math is off the developers are asking for around $0.60 per minute ($36 per hour) to keep playing once your energy is depleted and based on how energy cost per mission scales these numbers are only gong to get more insane. This is at least an order of magnitude more than any reasonable person would pay to play a flash game.
not a game and I see no point in giving some random dude on the internet $250+ for noticing that Kong has 40,000 games when that money could instead be going to the devs who make this site great.