When Facebook announced that it would pay a total of $19 billion to acquire WhatsApp, many were astouned by the price. Considering WhatsApp's huge and immensely engaged user base though, $19 billion doesn't seem as much anymore. Assuming an active user base of 450 million, Facebook paid around $42 for each of WhatsApp's users. The users of Facebook, LinkedIn and Twitter are all valued considerably higher if market capitalization and active users are taken into account. Was WhatsApp a bargain after all?