Too much.
The pgsql database is about 2 GB compressed, but it shares that with Nextcloud and I can't be bothered disentangling that right now.
But the picture storage takes the cake. I've disabled proxying images of other posts and pruned those that were proxied until then. I think. But still it takes up multiple GBs. I post many memes but not nearly enough to explain that. And because it puts all the images into a billion subdirectories it takes ages to even calculate how much storage is used. Dunno if it will be done by the time I'm done writing this post.
The picture storage is a huge black box. No idea what it's doing all the time. I can't shake the feeling that there must be better programs to handle pictures.
Performance is a big problem as well. I've only got hdds and all the constant synchronisation is hammering the database like crazy. Loading my own profile usually takes 2 or 3 tries.