and to answer your question, if u have a good history of earning $4.5k/month then you can sell your site for 2 years worth of earnings... if your site has unrealized potential then you can get more. and if you dont have a lot of history, then a site sells for 6 to 8 times an average month's earnings. if domain name is solid that would increase sale price too. also depends on pagerank, serps, active members, etc... too many variables to come up with a real estimate. need to know the facts or an estimate is pointless.
You have only 5 posts here at dp.. please establish some credibility by sharing references of sites for which you have worked this deal in the past by PM PS: its 2 million pageviews now !