BuddyPress.org

also, two other big factors are timeframe (ie. know your launch date) and number of people involved. generally, if you’re the middle person/project manager who reports to your c-level folks, they’ll want to put in their 2 cents — sometimes even conflicting feedback (eg. http://www.youtube.com/watch?v=EgDWwahgsYk … ‘bigger logo but feel small’ type of thing) which will also affect your timeframe/cost/marketing budget. there really are sooooo many factors that play into getting an estimate for a scalable website.