Right, there is a disparity — so, explain why it shouldn't instead be Comcast paying Level3?
Even if you want to privileged "sending" as being more charging worthy since you control what you send— in this case it's Comcast customers that have requested those bits, hosts connected to the level3 network are providing them.
Networks like comcast have built out imbalanced networks which likely wouldn't exist without their access to monopoly infrastructure. Practically anyone they peer with except other consumer broadband monopolists is going to be unbalanced.
Even if you want to privileged "sending" as being more charging worthy since you control what you send— in this case it's Comcast customers that have requested those bits, hosts connected to the level3 network are providing them.
Networks like comcast have built out imbalanced networks which likely wouldn't exist without their access to monopoly infrastructure. Practically anyone they peer with except other consumer broadband monopolists is going to be unbalanced.