If you clicked the link, you'd see he charges $1/user/month for teams with > 3 people.
I clicked the link and it was definitely not obvious how much it cost. I even clicked to add it to Slack and it didn't mention cost or anything. Pretty reasonable question.
It is $1/mo/user over 3 users. Says so on the FAQ.
Curious if they've tried other pricing models. Beyond, say, 10 or 20 users the value proposition shifts against that pricing model IMO.
Definitely worth experimenting with some more. I have some 15+ user teams that think it's worth it though :-)
I think halisaurus meant that the price is a bargain for bigger teams. I would agree - this could easily be worth more than 15$/month for 15 users.