I can personally recommend www.limelightnetworks.com
but honestly I havn't been shopping in a while. I would have recommended www.hostgrove.com
but they are out of business now (i know Steve personally). www.streamguys.com
does billing this way too (i know Mike personally) but not sure how much traffic you need to get seutp cos it's not listed on the site.
First figure out how many gigs you use a month, and then call LimeLight. I can vouch that it's the best bandwidth you can buy for shoutcast hosting I've seen. They use an edge distribution network so your listeners connect to a server that's physically closest to them, with servers all over the usa, europe, asia, etc. And they dont have any crappy peers like Cogent etc. We get five nines at LimeLight without a doubt. =)
If you call em let us know how it compares, I'm kind of interested in how they price low bandwidth. =)