It would have been a lot easier to focus on the important implementation details if the server was an off the shelf Lenovo datacenter server (SD550?) with a pair of 100 gig/s NVIDIA cards in it.

(Source: last month I set up a machine like this for a colleague to do approximately the same task. I spent "copy and paste the production server config" time on it, not a week.)

My main home server is a Supermicro SYS-510D-4C-FN6P. It has dual 25Gbps ports onboard but also an Intel E810-XXVDA4T with another 4x25Gbps ports.

Both of them are perfectly capable of saturating their ports using stock forwarding on Linux, no DPDK, VPP, anything, without breaking a sweat. Both of them were substantially cheaper than the machine in the article.

Is there something I'm missing? Why does this workstation need a ~$1000 motherboard and a ~$1000 Xeon CPU? Those two components alone cost more than either of my computers and seem like severe overkill.

Pathway to even greater corporatization and splintering of the internet?

Replacing public RIRs with private organizations, securely routing between each other..

How do I peer with the big corps in a SCION world?

Security and privacy are already addressed by things like transport layer encryption, so SCION doesn't really enable a more secure internet, it enables more (largely corporate) control