Website Launched 3 Months Ago, Only 2 Sales?

[Diddygonewild]

I started an educational training website, I'm an engineer and I developed a training video series for engineering software we use. The product is a digital download for $37 and very high quality but very reasonably priced. My site gets about 20 visitors per day, I am planning to increase this but everybody told me to test conversions first. I offer a free beginner training video series in exchange for their email then email market to them. I have a 6% conversion rate for my opt in, and have about 100 people on my list and am sending 1 email per week with tips and tricks then 1 sales email per month. I have only had 2 customers , should I be concerned? My list is growing fast, but everyone says to focus on growing your list. 2 customers out of 100 people on a list sounds bad to me.

Thanks for your advice!