Ahhhh, image posts are where your usage is going! Makes sense, my instance is just for my account and I don’t submit anything. Your postgres size is more or less in line with where mine was at your uptime. I’m using Docker Compose so I’m only considering the size of the volumes in my metrics, not the image sizes or anything.
EDIT: Turns out I accidentally firewalled my pictrs service, it couldn’t reach external sites to create thumbnails for external links. That’s why my storage usage was so much lower. Whoops.