>> "a team of 32 engineers (~ $500 million/engineer)"
Only if you consider the other employees worth/value to be $0.
An article mentions that Whatsapp spent $0 on user acquisition and marketing. If that's true, then yes, it's around $500 million/engineer.
Even if the company had nonengineers, it doesn't affect the ratio between revenue and engineers. The statistic usually does not imply that engineering is solely responsible for the success. Further, it generally can be hard to determine what portion of revenue is due to engineering versus marketing/sales, since the functions work together in a dependent way to make money.
Good luck creating an app used by so many without having a stellar support team.
Clearly this team has been quite successful! I can't agree say that they have almost replaced SMS, as many people communicate with me through SMS or iMessage. I have never used whatsapp nor has anybody a requested that I use it with them. As far as other messaging, everybody I know uses kik or Skype.
Congrats to the team of WhatsApp to build such a successful product in five years with a team of 32 engineers (~ $500 million/engineer). Reminder: They nearly replaced the SMS service worldwide.
Let's hope that the words by Mark Zuckerberg will be the truth and WhatsApp will be kept as an independent product in the future.