$150 for 3 years for just email is not cheap in my opinion. Also, it says closer to $200 for me but maybe it's regional. Fastmail is not a cheap provider. iCloud, Purelymail, Migadu, etc. are cheap.

You can certainly rent a mail-capable VPS less. Especially if you send emails through the AWS mail service. A small home server capable of hosting mail will absolutely not use 80W. It will use <10w.