This is kind of the number I was looking for -- "Cover your own costs: $1/year. Cover yourself and five other people: $5/year." I feel like something pointing out that the costs are around $1/year on signing up, maybe with a reminder once a year, would get most people self-funding pretty quickly.
And I was SOOO happy when I heard WhatsApp's business model: Finally, I'M THE CUSTOMER! I gladly signed up for the "free year" and started getting other people to sign up for it... only to have it bought by FB, and never charged my $1 yearly fee. :-(
Then I tried to get people to use Telegram, but hey never implemented encryption by default, instead implementing things like chatrooms with millions of people... then I signed up for Signal, but waited to see what would happen -- and they started doing some weird crypto thing. Thankfully that all seems to have not been an issue, so I might actually start recommending Signal.
