In my humble opinion: they are stealing you with that price for what it offers.

Buuuuuuuuuut, it's Mozilla, and I've been using Firefox for ~10 years, so this is my way to "pay them back". It also contains a super useful feature in my opinion called "Send", that basically if you have attachments that are too big to share through email, you can send them through "Send", imagine Mediafire for sending files, but inside your mail client, I don't use it that often but is useful when you need to share an .iso or something like that instead of a link to a cloud service.