Ask HN: What is the long-term value of a pre-beta email sign-up?

I'm working on a web app that targets small businesses and freelancers. We will eventually be charging a-la 37Signals pricing model.

We currently just have a single landing page at http://properprocess.com to collect email addresses.

We're doing testing on just about every element on the page using a self-learning multi-variate testing process I developed. One component of my algorithm requires estimating the long-term value of each email address that we collect (we call it conversion value).

I'm wondering if anyone has data on what percentage of people on a pre-beta email list turn into actual beta users?

And then what percentage of beta users eventually turn into paying customers when the paywall goes up?

I realize that there are many factors to consider, but I'm just looking for some help to ballpark the value of each email we get. This helps us figure out an estimated visitor value and tells us if various traffic sources are worth the cost or effort.

Thanks in advance for any insights!