If you're splitting 10gbit across 80.000 users, that leaves 125 kbps per user. Split it across 1 million users, and it leaves 10kbps per user. Sure, you could have more than 10gbps bandwidth from a single server to the Internet in theory -- but at that point I don't think sticking to 16GB ram makes much difference.
Millions of connections usually are websocket connections or HTTP keep-alive connections. In those cases there's no much traffic over those connections. Imagine game server for example. Latency is more important than bandwidth. 10 kbps is enough for many tasks.
I wonder how much of a hit typical web-socket use-cases would take from swapping to SSD? For games I'd think one might prefer just using connectionless udp, though?
