Comment by tabbott

The advertised pricing is for workplace use where the users are on payroll; if you read the plans page carefully you'll see we have free or highly discounted pricing for other use cases, both in Cloud and self-hosted.

Zulip is not designed to support 2M user accounts in a single organization. But if you enable the public access option (https://zulip.com/help/public-access-option), such that no account is required just to read content, you can end up with 1-2 orders of magnitude fewer "total accounts" that just wanted to see something once and don't actually use the server.