You're absolutely right. A serious part of managing SQL Server is keeping your costs down. RDS for SQL Server is so unbelievably expensive that I can't believe anyone uses it. I'm not aware of any meaningful extensions to MSSQL in the sense of TimescaleDB and friends either. I'll make the claim that we don't need Citus because everything they offer is built into MSSQL, and we don't need TimescaleDB because column stores are built in too, but if you did find some kind of deep extension you wanted to build, you can't do it. Simply not an option with MSSQL. You either build it outside of SQL Server, or you don't build it.