Netflix didn't buy transit from Comcast; they paid Comcast some large fee to upgrade links to one or more transit providers that Comcast would in the ordinary and traditional course of business done itself, so as to continue delivering its traditional unrestricted internet product to customers.
Netflix can't reach every Comcast node around the country, so it couldn't have 'bought transit' from Comcast. It did try the next best thing: colocating, at its own expense, servers at Comcast POPs with cached Netflix content. Comcast said no thanks to that one. Netflix also tried buying extra capacity from other transit providers (Tata and some others.) I think -- but am not certain -- that, when Comcast learned that that deal had happened, it began failing to upgrade those links, too.
It's hard to think of an explanation for these peering disputes between CDNs/transit providers and consumer ISPs that doesn't imply ISP hostage-taking. (Where the consumer is hostage.) These consumer ISPs have an easy job: keep these links to the middle networks and backbone networks up to date. And keep the copper in decent shape.