I'll spare you all of the details regarding conversion ratios, etc. since we've already covered that in part 1 of this series.
Ezine advertising is very much a viable way to pay for traffic, but don't use it until you've formulated a profitable ad in the PPC search engines. It's important that you know you have a winning ad before spending money on ezine advertising. Use something that's proven to get results.
Ezine ads can be purchased at reasonable rates and the cost will vary from one ezine to another depending on the newsletter's circulation, track record of producing sales and the exposure that you'll get.
By exposure, what I'm referring to is the type of ad that you buy. Your options typically include solo ads, top sponsor ads, middle sponsor ads, bottom sponsor ads and classified ads. A solo ad is sent in an email with no other distractions. You get all of the attention, and for this reason it's also the most expensive form of ezine advertising. Top sponsor ads allow you between 5 and 8 lines of copy and are included in regular ezine issues near the very beginning of the newsletter. Middle sponsor and bottom sponsor ads will be similar to top sponsor ads with the exception of the position within the newsletter. And lastly, classified ads are usually shown in groups near the end of a newsletter and are the lowest cost.
My personal opinion is not to advertise in ezines that you haven't subscribed to. If you're considering advertising in any particular ezine, subscribe to it and read it for a few weeks before spending any money there. That way you'll be able to get a feel for the value of the content, the kind of reader that will be interested in the publication and whether or not the advertising opportunity is a good one.