ppc+email marketing question

Hey guys....
this question is for marketers that combine ppc with email marketing.

I have read a lot of books and posts about ppc and email marketing and from what i understand the best and most profitable approach to make money is to combine the two:
- use ppc to acquire subscribers and increase the list quickly.
- use email list to market to people over time and build a relationship that would eventually make them customers and increase conversions.

My questions are:

-the way i see it, the numbers just don't add up:
as you move down the sales funnel your eyeballs seeing the product decreases:

*as i understand: on average: only 30% from people clicking your ad opt in to the email list.
*as i understand: on average: only 5% of people on your list click on links in emails and go to the sales page.

so only 1.5% of the people clicking the ad go to the sales page (0.3*0.05) and that is before even buying the product so the number of people buying the product is even lower.

now, because this percentage is so low, and because obviously there are a lot of people that don't buy, a lot of people that don't open their mail and so on...to make a profit some people would have to be repeated customers and repeatedly buy what i sell weather by recurring services or buying several different products. Am i correct? Do you have repeated customers in your list? i don't know...from my point of view it looks impossible to make money this way... i would really like to have some help and guidance from some of you that uses this method to make money.

- are you using other niches other than making money niche? it's like everywhere i go the only niche i ever hear about regarding email marketing in this forum and in other marketing forums is the making money niche...even when i wanted to buy sollo ads...the only niche that was available is the making money niche...

any help will be appreciated....
thanks...