Actually, no, Comcast's paid peering costs are significantly cheaper than all but the lowest quality transit. In other words, if you just have Cogent, you get what you pay for.
That may be true at the 10G level (which I didn't price), but isn't true (in my experience) at 1G. Plus, it's a lot more likely that you'd want 10G of transit and 1G of comcast than 1G transit/10G comcast, so per-G, your decent quality (Level(3), nLayer, etc.) transit is going to be cheaper. Comcast also seems to negotiate less, since they're effectively a monopoly on routes to themselves, vs. transit.
(Obviously the right thing to do is grow to needing 10G of comcast and 50-100G of transit...)
