For the internet radio station I work with (radiovalencia.fm), we're currently paying streamguys.com $80/month for non SSL. It would be $120/month with SSL.
But my major question is for a site like my radio map:
http://goodradio.org/map
That links to about 110 different college and community radio stations, most of whom aren't streaming with HTTPS. Since Chrome blocks "mixed content" (embedding an HTTP stream from an HTTPS page) there's currently no way to make that webpage be https.