Peering links between backbones (like Level 3 and Verizon Business) are supposed to have equal ratios. Peering between content providers and end-user ISPs don't care about ratios.
Right. If they really cared about ratios they wouldn't offer unbalanced service such as 50/15. They have built their network around users predominately consuming content and then complain when there is too much consumption from specific providers that happen to compete with services they also offer.
An end-user ISP like Comcast has a monopoly on access to their customers, so if they're allowed to charge for peering there is no competition to limit how much they charge. This tends to result in the ISP allocating 99% of the surplus created by peering to themselves.
That's very true. The only limit would be losing customer (HA!) because they didn't connect to the right content providers. There's some interesting network effects here that smell like positive externalities, which would explain the underinvestment. But also suggest that there isn't a good solution.
