I send 5Gbps to an eyeball network (let's say Comcast, for the sake of discussion) it might cost me $5000/month to do that through my transit provider (intentionally inflated cost). Comcast will interconnect, settlement free, to networks who exchange 7 or more Gbps. Three optics and three cross connects are $3000 + $600/month.

How much is that additional 2Gbps of traffic (to Comcast) worth?