You can charge whatever the market bears. Try to find
that certain price point where your ads sell well at
maximum profit. For instance:
Back in the days when I used to sell advertising in my
newsletters, I initially set prices that I figured were
in-line with other newsletters in my market. However, it
soon became clear that the prices were too low -- at one
point I was booked 10 months in advance, before I stopped
accepting ads!
So I raised my prices... and raised them again... and
raised them again, until ads were booking no more than
4-6 weeks in advance. That gave me a comfortable booking
margin so that I wouldn't have to worry about filling my
ad slots... customers wouldn't have to wait nearly so long
to have their ad run... plus I made far more profit than I
otherwise would have.
To find out a good starting price for your ads, you'll
want to take a look at what similar ezines are charging.
I think the best place do so is at the
Directory
of Ezines -- it'll cost you a few dollars for a membership,
but it's the most up-to-date directory I've found, and it can
save you loads of research time. If you don't have the bucks,
go instead to another ezine directory such as
NetterWeb.
When setting ad prices, there are other factors to take
into account such as the number of ads per ezine, the
location of the ads, how often you publish, whether you
have a 'no competing ads' guarantee, and more.