You may want to investigate CDN services from CCBill's sister company Cavecreek. I don't know the costs but they do offer a whole suite of internet services for adult sites. If you have your site hosted by Cavecreek you will also get a 1% reduction in your processing fees from CCBill.

I have used Cavecreek since the beginning and haven't had a downtime issue ever and their tech support is quick to respond.