I want to thank everyone who replied. I did some research on most of these and think PurelyMail is the winner for me. Feel free to correct me if I got some details wrong. I want to give a shoutout to @mbirth for mentioning Disroot, which looks like a really interesting experiment in federated services.

Also, I know this post is really bending the rules for c/selfhosted, but connecting your selfhosted services to an email provider is essential, and having a reliable and affordable email provider just makes this weird hobby of ours a little easier.

My Rating (1-5)	Service	Website	Annual Cost	Only Email?
5	PurelyMail	purelymail.com	$10, pay for added storage	Yes
4	MXRoute	mxroute.com	$50/year small plan	Yes
4	Disroot	disroot.org	Free, pay to add storage and domains	Yes, separated from other Disroot services
3	Fastmail	www.fastmail.com	$60 individual plan	Yes-ish
3	Mailo	www.mailo.com	~$14 premium plan	No
3	Proton	mail.proton.me	$48/year plus plan $120/year unlimited plan	No
2	Mailbox.org	mailbox.org	~$14 light plan ~$42 standard	Light plan
2	Migadu	migadu.com	$90 mini plan	Yes
1	GMX	www.gmx.com/mail/	Free, ad supported	No