I expect this may be down to the terminology. Sybase always used to quote huge numbers for DBA:database ratio compared to Oracle. But what Sybase refers to as a "database", Oracle just refers to as a "schema", and there can be as many schemas as you want within an Oracle database.
And even if it is 1800 physical servers... If significant fractions of them are identical, they really should only be counted as one database cluster with so-many nodes.
And even if it is 1800 physical servers... If significant fractions of them are identical, they really should only be counted as one database cluster with so-many nodes.