Then it becomes my job to keep said system, anti-spam settings, etc updated... I don't want to do that work... Frankly if I didn't have to work for a living, I'd start a new open-source mail system that didn't suck.

I typically don't send more than 40 emails a day. But have several domains I would like to have email for... paying $10/address is a bit steep to say the least for that use case.

Here's my anti spam solution. I created an entire ___domain for it with a catch all address. When I sign up for a service I use [email protected], if I get a lot of spam I reject mail for that address at the server.

You are paying for convenience here.

but what about their deliverability / spam score?

You get a dedicated IP only for you. Never had a problem in the past 2 years or so.

This is good. What I meant is that you have to check your IP reputation by yourself, while this provider does it for you (if I understand correctly), hence an extra charge

Beware that Digital Ocean blocks all traffic for outbound SMTP on floating IPs: https://www.digitalocean.com/community/questions/floating-ip...

This pretty much breaks the entire usecase, as you cannot build an IP reputation.

Floating IP's are not the same as the dedicated IP you get from the VM itself. I've been sending outbound on that for the better part of 2 years.

To the other point, if you have a problem with spam scores, you are probably sending too much mail for this sort of solution (consider Mailgun 10,000 emails/month for free). For an individual it is fine, not for use as a mailing list. A clean IP address (every IP I've ever tried was clean), DKIM, and SPF will allow you to hit pretty much anybody. It might take a few people pulling you out of spam on gmail before you can send to them, but I think that's true of any new mailserver.