Well lower TTL means less caching which means less bandwidth savings which means more money to pay?
Correct me if I'm wrong, but isn't the bandwidth cost not as much of an issue as it was, say...3 years ago? I remember when you had ISPs with data plans that were by MB and more recently by GB. Now, streaming that sort of content over the net requires much less bandwidth due to the content packaging that I wouldn't think the cost would be that high...
BUT, I fully admit, I could be way off base - it has been some time since I worked closely enough with an ISP to know specifically on the exact details.