There are other reasons for the networking costs
Well, while I have considerable respect for James, I have to disagree with him somewhat.
Networking equipment itself is also generally following the Moore's law. Networking equipment cost != networking costs and this is where he is being a bit disingenuous.
Most cloud providers tried (inclusive of Amazon) to do DIY networking done by software engineer as a replacement for proper resilience which is using algorithms and protocols for which there is a mathematical proof of convergence.
For Amazon this cheapskating experiment ended up in the majestic clusterf***s of 2013 when they had several zone-wide outages due to unhandled network failures.
From that moment onwards Amazon has been buying proper equipment to augment the DIY. This expense however is a natural result of a failed networking experiment (for which James should do some Mea Culpa) combined with a failed design (again, Mea Culpa needed) and the cost of fixing it (again - Mea Culpa James). It is not your normal purchasing and cost curve to which Moore law should apply so he should stop complaining.