What would Netflix be losing? A lot of customers? And handing all of them over to Comcast's on-demand service. It'd be a massive win for Comcast.
There's no net neutrality issue in this discussion at all. Comcast is simply declining to upgrade its peering with Cogent. How is that net neutrality? If Netflix comes to me tomorrow and decides to buy all their transit through me, is Comcast somehow required to give me lots of free peering?
Netflix might be the majority(?) of Cogent's traffic, and Comcast might decide that it's not worth upgrading the connections for them. But as long as Comcast isn't discriminating traffic on their end (via some traffic shaping mechanism, I'd guess), then it's simply a matter of "Comcast thinks Cogent has enough connectivity, and sees no reason for them to upgrade the connections while getting nothing in return".
Their customers may disagree, but it up to them to not buy the service. (Perhaps the real problem here is lack of competition in the ISP market?)