To make a substantial amount of money all they have to do is monetize 1,000,000 messages,not users,but messages/day. To give an idea as to the number of messages sent on a chat app see BBM.
Over 60 million BBM users send and receive an estimated 10 billion messages per day
1,000,000 messages at 45 cents/message gives us revenue of $450,000/day.
Seems ridiculous doesn't it?