Why WhatsApp is worth $19 billion

WhatsApp may be "cheaper" than most rivals: Facebook paid just $30 per Instagram user at the time (the service had 33 million users when Facebook bought it, compared to 150 million today). Facebook is spending $42 per WhatsApp user. But given WhatsApp's enormous user base, its purchase price might be a bargain compared some of its competitors. LinkedIn's (LNKD) share price values that professional social network at $153 per user. Twitter trades at $140 per user, and Facebook is at $123. Even at its latest $2 billion valuation, Snapchat trades at $50 per user. (And Snapchat reportedly turned down a $3 billion offer from Facebook last year.)