If I got 1,000 visits per month to an ebook site through content marketing, I could only count on about 2% joining my email list, and around 9% of those ever buying (3% across three pitch emails). Multiplying those, content marketing would only drive 1.8 sales per month. Clearly some people are finding much more success than that - which of these numbers is off?
You have the variables right. The values are all going to depend on your funnel design and effectiveness. You look like you are using an e-book as your lead magnet to get people to register. I would suggest you would only want to give them that e-book if they provide their email address, which drives your initial lead opt-in. From there it's your job to have more offers for them in order to make sales. You would have a thank you page offer for activation and then you'd have backend offers for higher dollar services or products now that you have activated some of the customers. You can also get more complex with different email campaigns and branches depending on their behavior in the funnel.