The first is e-mail.
The second is an extremely hard-to-validate promise of future work, such that (a) cutting-edge security and privacy protections are maintained; (b) properly designed regular backups and redundant infrastructure ensure your e-mails won't be lost; (c) staff ethics, training and oversight will protect against insider threats; (d) protection against spam and phishing will be effective - but will not block legitimate e-mails; (e) e-mails you send will get delivered and not marked as spam or silently discarded, even when sending to the likes of gmail; (f) no e-mails sent to you will be silently discarded or otherwise lost; (g) if issues do arise, that they will respond promptly and competently; and (h) as webmail technology advances and market conditions change, they will keep up-to-date and stay in business.
There's no way for me to validate most of these things. Instead, we rely on a supplier's "reputation" - an amalgamation of their past performance, their visibility and their marketing.
There are many e-mail providers. There aren't many e-mail providers widely known as reputable.
In other words, Fastmail doesn't face much price competition within the market of "e-mail services recommended by users of Hacker News" even if they do within the market of e-mail services generically.
The killer is five nines availability. That's pricey.
I used to run mailsystems and maintain mailsystems code in the 1980s. I don't do it now because it has too many moving parts. I got a grandfathered domain into hosted by Google and it's worth a damn sight more than the apparent market force bottom price.
Hardware or software or service your competitors have to be comparable or at least bearable to apply price pressure. I do not judge fastmail as price competitive because they (like apple) are competing in quality. Not price.
By the way, I was asking for the point of view of an expert. If you are not an expert on email services, then I have no interest in hearing you speak condescendingly to me.