An article in Advertising Age talks about the cost that advertisers must pay to run advertising in Television spots and the Insertion fees they must pay. This fee is a holdover from days long gone when running an ad in a broadcast actually required some person to queue up a tape.
So as a Podcaster when you are talking to a media buyer one thing you will want to say if you are on the edge of making a deal happen is to mention that in the podcasting space there are no insertion fees to contend with as the mainstream media will invoke in their advertising pricing.