Still, it's a good idea to put some number for anchoring, and the current average is not a bad one. And a number that seems to come from other people could be more influential than a "recommended contribution".

Edit: As others point out, there are already some other anchoring points on the page, so having an average lower than those may be hurting them. It might have been wiser to make the "Top contributors" tab the default (or only) tab in their realtime stats display.