It doens't matter if 9000 are inactive. The numbers are what ever Webmaster goals for. 10,000 members looks very good on a resume.
It a reputation thing. At first look, it's very impressive if you don't know how many are actually active. Which even still is very high. Once Predators rolls around, we can expect something like maybe 13,000 members and like 200 online at once. No doubt.