On Business Week Heather Green explores some of the possibilities to make money out of podcasting. Sponsorship is at the moment the most used business model and it's usually based on a flat rate deal with the advertiser. Sponsorship implies a 15 or 30 seconds audio ad at the beginning of the podcast. Of course, as the article points out, if the ads are based on a flat rate, they can end up being a bargain or a total failure, depending on the number of downloads the podcast will receive. Prices per thousand downloads range from $10 to $25, with podcasters taking advantage of the fact they reach specific target groups. The more selected the audience, the higher the value for the advertiser.
However, several podcasters want to stay "pure" and avoid advertising to make money out of their audio files. Some are asking for donations (even $2 can help) or charging subscription fees.