The prices below are for an organization, never for a person. Personal accounts are free. You can belong to as many organizations as you like, and write as many documents as you like on your personal profile, without paying anything.
An organization only pays for the people who join it — a seat is counted where someone is a member, so the same person can be a free member of one organization and a paid seat in another.
Hobby
For individuals and small teams getting started.
Professional
For startups and small businesses that need unlimited scale.
Enterprise
For large organizations with on-premises deployment needs.
Open Source
For projects that build in the open, at no cost and no member limit.