Level 3 is paying Comcast because the alternative was for Comcast to let the peering links congest, which would hurt Netflix streaming performance. Basically Comcast has a new business model for their Internet service: Everyone pays Comcast and Comcast pays no one.
Yeah I can't believe this works for them. So I assume Comcast pays Tata, right? I was under the impression at some point that was their primary provider (paid transit). They keep these links so congested [1], that in order to actually provide reasonable service to Comcast users, a content provider needs to pay to peer with them (or pay someone else to) in order to give reasonable performance. I guess if you have enough users and enough of a demand to reach them faster, you can charge others. I take this to mean that Comcast should be paying me to subscribe to their Internet service! (or at least to watch Netflix on their network)
Edit: Although it is not my exact area of research, a colleague of mine has done some interesting work that discusses the costs of P2P traffic for some of these ISPs that is somewhat related: http://torrentfreak.com/large-isps-profit-fom-bittorrent-tra...
