I think it's actually a quite complicated question and it only works because people are playing somewhat nice with each other. Like imagine if Netflix refused to peer with one particular ISP unless they paid an extortionate amount of money. Should the ISP be legally required to pay any price they name? I don't think that would be fair.

One solution could be to have geographically distributed test points. Any connection to be able to claim a certain speed has to be able to get that speed to those test points. And the test points are legally required to connect to anyone that can bring fiber to their doorstep. If someone plays hardball with peering there will then always be the backup option of routing traffic through one of the test points.

Idk, just throwing out ideas here.