How much price can be asked for a Good Ranking Website? What is the theory of pricing?

Dear warriors,

I have an 8 months old website which is doing really really great now in Google and in revenue as well. On this last February I have started a news journal and put some good works to make it work. After all it was my first experiments with adsense and 'seo to my own' website. I've done optimization to many sites but never tried it by starting a few websites myself other than our corp. page (it ranks #1 on Google for 'quality seo')

Okay coming to the point. While thinking about selling a website what are the factors that has to be considered? The news journal (its a press release website) I'm talking about has got many good keywords (including the most competing 'free press release') in the first page of Google. It has daily 300-500 page views and 60% ++ from Google for different keywords. Though it is not bringing 1000s of dollars monthly - it has good adsense income. Now 4-5$ a day. And there are other income as well - like paid submissions, links banners etc. Nearly a 300+ USD per month and yeah, it's increasing per month. I've got just 30$ before 3 months in fact.

Now I have a plan to sell the site. But I'm confused about the price. Normally I think it can be a ten to fifteen times of the earnings per month. But this site also have good SERPs for very competing keywords.

Kindly leave your suggestions and advices - and yeah this is going to be my first website sales.