Looking for stats for input sizes of at least between 4 and 30 MB.
To my knowledge, there are no published stats, but as Gandalf suggested in the comment on your question, you can test it yourself. To get the stats I would recommend using the DBMS_PROFILER package which times lines of PLSQL down to the nanosecond.
A quick primer on DBMS_PROFILER cribbed from Oracle PL/SQL Programming by Steven Feuerstein (published by O'Reilly):
Install scripts (for your DBA): $ORACLE_HOME/rdbms/admin/profload.sql
Install scripts (for your schema to capture stats): $ORACLE_HOME/rdmbs/admin/proftab.sql
scripts for reporting (for your schema): $ORACLE_HOME/plsql/demo/profrep.sql $ORACLE_HOME/plsql/demo/profsum.sql
to profile:
Begin
DBMS_OUTPUT.PUT_LINE(DBMS_PROFILER.START_PROFILER('tag value for your run'));
your_procedure_to_test();
DBMS_OUTPUT.PUT_LINE(DBMS_PROFILER.STOP_PROFILER());
END;
to get reports, run one of the queries in the scripts for reporting.