I didn't say people are not willing to pay money to use an app that has free alternatives. I said good luck finding 2 billion such people. Whatsapp today is used by everyone. 8 year old kids and 85 year olds. The network effect. Its biggest asset is the number of users which makes it easy to communicate with everyone you know on it (not everywhere but in many countries). If they charged money it would've been different. It's not about the money. Everyone can afford $1/year. Even kids in poor countries. But not everyone has access to a credit card for example. Many wouldn't bother and use a free alternative like FB messenger or Telegram or whatever.