Interconnect agreements are different than "fast/slow lane". CDNs will need to pay a premium so that their traffic will not be slowed down, regardless of the peering agreement.
Interconnects are exactly what the "fast/slow lane" argument is about. Netflix bought interconnects from Comcast and Verizon. Just through buying interconnects to the ISPs, the CDNs ensure their traffic won't be slowed down by an intermediary like Cogent.
They're not intending to provide higher QoS for sites that pay up -- that's insane and it wouldn't work anyway.
It's my understanding that interconnect agreements solve congestion on the network by having a larger connection to infrastructure.
Fast/slow lane practices throttle that connection, regardless of how large the pipe is.
So, my small business website could be using a large internet connection that technically has plenty of bandwidth to carry my traffic but, unless I pay Comcast a premium, traffic from my website will be put in the slow lane and throttled back.
Then your understanding is incorrect (sorry; not trying to be flippant). Interconnects are the entire story here.
The media has framed a lot of the congestion issues in the context of "fast/slow lane" but what they come down to are business disagreements between the transit providers and the ISPs. The solution to these disagreements from the viewpoint of a large service provider is to purchase an interconnect directly to the ISPs. If you are a small service provider, the solution is to purchase delivery through a CDN. Netflix used to purchase delivery through CDNs until it got too expensive for their business model; so they started building their own CDN that they called "OpenConnect". They used their positive brand image in conjunction with the ISP's poor brand image to launch a PR campaign with the goal of knocking down the price they would have to pay for interconnect service. It worked; they knew they were always going to have to pay the Comcasts and Verizons of the world but they were able to talk the ISPs down a significant amount.
Strategically, it's a bad position to be in for a service provider because the ISPs can raise the price at any time (which is why Netflix has continued complaining about it). But realistically, the ISPs sit on such a strong market control point that nothing can really stop them from setting prices (common carrier status just means they have to offer the same price structure to everyone; not that they can't arbitrarily raise prices).
