I'm not sure saving $2 a year is worth using a self-proclaimed (according to its website) beta service. Then again Gmail was in beta for many years.
In my opinion, the fact that people would pay more for Netflix than their email provider is kinda crazy, when you think about their relative importance.
But I think Netflix is extremely cheap/good value if you enjoy the content.
PurelyMail seems to charge by storage, not mailbox address; and AFAIK so does Migadu (which, up until reading this post, I thought was unique in that).
They do allow infinite aliases which covers most of my needs, but when I wanted to use a FastMail box for my home automation system's service account it didn't make sense to do so.
Not exactly the same as hundreds of individual addresses/inboxes, but may fit some people's needs.
I've been using Zoho like this now for a little while and I am pretty happy with it considering the price.
There is an undocumented limit though. You can generally only have upto 30 aliases.