What needed for using PBI Report Server in production environment

You will need licenced for both components:

-Power BI Report Server

-SQL Server DB

For Power BI Report Server you will need SQL Server Enterprise Edition with SA licence (minimum for 4 core) or Power BI Premium (minimum is 8core).

For SQL server is enough SQL Server Standard Edition without SA.

There more option how to setup enviroment:

-you can install both on single machine (not recommended for production) > you will need only SQL Server EE with SA for number of cores of machine

-you can install on two (or more) machines (recommended)> you will need SQL Server EE with SA (or Power BI Premium) for PBI servers, and SQL Server SE for DB machine.

-you can licence entire physical sever with SQL Server EE with SA, and there run multiple virtual machines, some for SQL Server, a few for Power BI Report Server (and later some with SSAS)
-and so on