Everything I'm seeing about hosting costs in the current day and age is that the full AtProto stack (PDS, Relay, AppView) is roughly in par with hosting an ActivityPub instance of equivalent size (if not a little cheaper).
And with AtProto, folks get to pick and choose what slice of the stack they wanna host, and opt-in to more of it gradually as they see fit. With ActivityPub, you are either opting in to hosting an entire instance, or fully reliant on someone else.
I'm open to the idea I'm misunderstanding some aspect of ActivityPub, given I've not really explored the hosting side of all that deeply.
My self-hosted mastodon server continues working, and can continue federating with e.g. chaos.social
With bluesky it's different.
If I am fully self-hosting the entire bluesky app, I need to spend ten thousands of dollars a month, but it'll keep working.
If I self-host my own app, it's cheap and keeps working, but I can only see content from my users in the best of times.
If I use bluesky's relays, it's cheap and shows everyone I follow, but it'll stop working if bluesky disappears.
> If I am fully self-hosting the entire bluesky app, I need to spend ten thousands of dollars a month, but it'll keep working.
That strikes me as a point in favor of AtProto for decentralization (unless it's possible for others to cheaply/simply run their own backups of the entire mastodon.social instance & I'm just unaware of that fact).
> With bluesky it's different.
The key AtProto differentiator I find most compelling (which it seems you omitted from your list) is that Bluesky can disappear tomorrow and, if I'm running my own PDS, I can simply log in to another different platform using my same username & account and immediately see my entire message history w/o skipping a beat.
From the standpoint of an individual user who just wants to own their own data w/o needing to worry about hosting entire apps or manage scaling, the fact that AtProto allows me to host a PDS and do just that while still using any of big-name apps w/o needing to create new logins and fracture my online presence feels like a far more pragmatic trade-off, IMO.
I guess it comes down whether you care more about data decentralization, or platform decentralization. Personally, I care far more about the former, and to that end the AtProto model feels much easier to set up & far more seamless in practice.