Hey, yeah I actually was going to see if I could post the full setup and cost on this later, but since you're asking now I'll just go ahead and post it here!
The domain - programming.dev - cost $560 or something like that for the first year, then it's $427 for every year after.
The lemmy instance is running on a Vultr High Frequency instance at the lowest tier. I thought I could up it if we started getting high traffic, but expect the server to run just fine for quite a number of users. I do think I might have to move postgres off to its own dedicated instance, but haven't really thought too much about that yet.
I think bandwidth is actually going to be the biggest issue, because if we federate with other massive instances then even if there is only a small number of users, we're pulling in all the traffic from the other instances. I can definitely understand only allowing a few instances, but not sure I'm going to restrict that just yet. If people can donate then that shouldn't be a problem.
The email is all running through SendGrid. I was going to use Mailgun, but Sendgrid is a bit easier to use and has a lot higher cap, and I expected to get to that in time. Currently SG costs nothing, but I expect it to cost $35 a month after my trial runs out...