Yeah, I think that's basically right. If you know AWS/S3/CloudFront or Cloudflare Pages or whatever, the raw hosting cost is close to zero. That's not what I'm charging for. It's more the boring workflow around it: give someone a WordPress editor, keep WordPress private, export the static files, handle backups/deploys, and make it one thing instead of a bunch of docs and scripts.

You actually said it yourself in your comment: "not everyone can deal with AWS, nor can everyone edit a website." Stelae is for the second group, the WordPress-editor side, who don't want to run public PHP to publish. The €19.90 isn't margin on the hosting; the hosting is yours, on whatever provider you pick.