It IS relevant to this case. Extra peering connections cost 0, zilch (besides the actual hardware cost which is really minimal if you're just popping in a cable into an existing switch)
At the peering centers, after the obvious monthly colocation fees you simply pay for YOUR traffic towards the Internet (upload) and for YOUR to be reachable across the Internet. You don't pay for the amount of data you transfer, you pay per Mbps that you upload disproportionate to what you accept.
So Netflix is paying an amount of money to upload their data, Comcast gets it for free, if they would actually accept the data, it would reduce their peering costs (not by a whole lot but a couple of thousand/month at least). The problem with Comcast however is that Netflix is disrupting their side business (cable etc) so by spending money in blocking Netflix they hope to recap that by more cable subscriptions.