I'm admittedly not versed in the AT protocol, but $30/month is high for me. Something like $10/month is quite fair, and i would expect should be more than enough for a VPS to host my and 2 other members of my family for any social network service...This $10/month is overkill for other servers on the ActivityPub via say gotosocial, pleroma, etc. Not that ActivityPub is perfect or anything like that, i just mean that $30/month is not yet what i would call a sweet spot for self-hosting something...but of course, that is absolutely leagues better than any cost that the bluesky team or other bigger players would naturally have to pay for ongoing infra., etc.
Then again, i will not deny that there's also the possibility that i am simply cheap! :-)
Right, but a Relay is literally a network-wide optimization. That's why in my other comment I'm mentioning that it's hard to do apples-to-apples comparison. With Mastodon, you only have one possible role: "hosting an instance" (which is like hosting a mini-Twitter with almost no data). ATProto aims higher in terms of UX (shared world by default) so there are different distributable pieces with different incentives to run. Anyone can self-host a PDS for super cheap (which will store only your data). But running a Relay is useful as an optimization for whoever's running the actual backends. So if you're a company building on ATProto, maybe you run your own Relay just in case (or maybe you don't and reuse an existing one). Or if you're a collective of people, maybe you pool resources together to run your own independent Relay. It's not something you'd just run for yourself unless you're a huge enthusiast.
Then again, i will not deny that there's also the possibility that i am simply cheap! :-)