Hope this provides a somewhat "relative" look:

Sun 3800 w/4 processes
25M logs (and I'm doing an aggregate, you're not). I searched through 5 logs which brought me up to 125M total.

SELECT seg_owner, seg_name, count(*) AS Hits
FROM v$logmnr_contents
WHERE seg_name NOT LIKE '%$'
GROUP BY seg_owner, seg_name;

Took me about 3 minutes