To be fair to Temptress Games, the way I understand it is that if you want the game and don't care about other perks, you can subscribe for just a month and get all episodes currently released. Then, when a new one drops, you subscribe again and get it as well.
But many force you to go to the £8 or £16 a month to get the update, not the £4 one! So that is £16 to £32 to get an update that may be 20 minutes long!