A lot of this depends on what you're selling, and your conversion rate (which will depend on exactly how you got those subscriptions).<p>Is the newsletter geared towards database administrators, who gave you their email address because they wanted to be notified about new developments in their database of choice? Your conversion rate for a database-related product will probably be high, while conversions for a whitepaper on writing your own ebook might not be.<p>How did you get the subscribers? Are the products you're trying to sell geared towards their niche?<p>If all you want is a mathematical formula, I like to take a pessimistic approach like so:<p>subscribers * 0.25% conversion rate * cost of product = revenue<p>If it's ads in your newsletter - I have no idea.
It sounds like you want to know how much you should charge for advertisements on your newsletter. A good way of determining this is to see how much others are charging- pick a newsletter similar to yours (content, popularity, etc) and contact the owner pretending to be an advertiser (they usually won't disclose their rates otherwise). Once you have that info, price accordingly.
It depends very much on the audience of the newsletter.<p>But you'd be looking roughly in the region of $5-$15 CPM unless you had a particular niche that advertisers really wanted to reach.