Every so often Ira Glass requests donations at the beginning of the This American Life podcast. In episode #370 (aired 22-DEC-2008) he said it costs “…over $150,000 just for the bandwidth each year”.
Why not use BitTorrent? TAL podcasts are available only for a limited time, usually one week: this should ensure many seeders. The podcasts last about an hour and are generally a 30MB or so .mp3 file.
One issue with this is–as far as I know–no feed readers can speak BitTorrent. Here’s one thread I found discussing this topic.