> There are honest atproto digs out there but that is not one.

Which one? The expense, or not being decentralized? The latter remains valid because the majority of the userbase chooses ("only" by default ofc) to coordinate through a single operator. Network effects mean that you either play by their rules or you aren't allowed in the garden.

It's good to learn that a full mirror is so cheap but I think the criticism still holds to the extent that it's a high enough price that unless something changes it will continue to discourage the network from ever becoming truly federated. Compare to activitypub where you can stand up a fully self sufficient node on more or less anything that's capable of networking. The obvious downside being that the network is more fragmented and often less reliable overall (ex nodes are regularly flaky or go missing entirely, no single unified view of the network, etc etc all the perfectly valid complaints about AP).

I think AP, AT, and nostr all get certain things right but all have major downsides baked into their designs. Note that I don't mean this comment to be negative, merely to respond to your remark that the dig in question is somehow invalid.