Zotero storage? Depends. Zotfile doesn't work for attachments in groups and it doesn't work for webpage snapshots. Also, images in notes count towards your storage (or may in the future, not sure). Syncing the metadata, though, is always free. So for most non-group users, the answer is no, but there are scenarios where you will get >300MB without PDFs.
So for most non-group users, the answer is no, but there are scenarios where you will get >300MB without PDFs.