WhatsApp provides more than $1 of value to me in a year, provided I have already decided to use it. But paying a subscription also represents a psychological commitment, a loss of choice for a year, a mental tracking cost if I should reevaluate annually, an effort cost to convincing others to use it if I want to communicate with them, and an opportunity cost. Because I'm certainly not going to pay $1 to 10 different IM apps though I may keep 10 if they were all free.

The strain of all these hidden costs is way more than $1, probably on the order of $30. So WhatsApp reaps $1.5B and dumps $45B worth of externalities on its user base. I refuse to pay.