The cost of downloading WhatsApp on iTunes is only 99 cents, and on other platforms is available for free. But there is a catch, WhatsApp is free only for the first year. Second year onwards there is a fee for $1.99 for a period of 3 years, and this is where they are going to make money. Currently WhatsApp has over 100 million subscribers, and suppose 80 million are non-iOS users, they will earn a cool $160 million easily.