It's expensive if you think of what it costs to keep a mail server online. They have a price that clearly shows to me that they have no competition.
But I do believe that even these cheaper ones are expensive for what they provide in terms of storage capacity, number of aliases, etc. Costs are supposed to go down over time, and prices too.
(your FastMail subscription also goes towards paying for work on improving the standards and developing open source software to support them)
https://www.scaleway.com/virtual-cloud-servers/#anchor_start...