The customers of A are paying A to access to the internet, including N. So A should charge their customers enough that they can pay for the equipment to deliver that.

In a working market with many participants, customers can choose a cheaper ISP that has congested/throttled peering, or a more expensive ISP with gold-plated interconnects.

The problem is that in the US, typically your choice of ISP is limited by geography. In many other places you have open fiber networks where the last mile is shared and then you can choose what ISP you want ontop of that, and the ISP is what determines how good your peering is.