Odd that you couldn't reply to me, but HN is a strange beast.

Users were paying for Whatsapp [1]. I believe that data point illustrates that users would pay $1/year for a chat service, but this is just an opinion until someone decides to stand up a new service and charges for it.

[1] The evolution of WhatsApp - in rumours and revenues WhatsApp had dabbled with the subscription revenue model in 2014, which amounted to charging an annual $0.99 membership fee, and earned above $1 billion in the first nine months of instating this fee. But following their $19-billion acquisition by Facebook, they came to revoke these charges, and WhatsApp was a free ride for its one-billion-strong and counting user base again."

https://yourstory.com/2017/03/how-whatsapp-makes-money/