Hacker News Reader

Its part of the remote-only and open source oriented culture. Haven really good written communication - which documentation is, really helps when you are spread all over the globe.

vs how much $ cost in salary they save because new employees can look things up in the documentation instead of asking colleagues or figuring it out themselves.

I think part of this also contributes to their brand (open source first/foremost) and to potential contributors so there's more to the equation than just impressing potential customers