Resurfaced the traffic numbers with the team, let me see again if we can dig them up.
stats for all NixOS and Nixpkgs releases (i.e. all the store-paths.xz files on releases.nixos.org):
Done! Found 51360806 store paths, 384085 GiB uncompressed size, 93618.1 GiB compressed size, 58.3715 GiB estimated .narinfo size
#thanks to @edolstra