Their primary storage medium is block storage which is quite expensive. Codeberg cited it, although post-hoc, in their decision to ban AI projects. GitLab runs (or ran) the large block storage based Git service I know of which is Gitaly.
If you want to achieve public service level traffic and cost then you pretty much need to find a way to leverage object storage.
Note that this assumes cloud-based. A rack full of hard drives is far cheaper per GB than either, even at 50% utilisation and 2x redundancy. (It would have to be! Amazon obviously wants to make a profit)
If you want to achieve public service level traffic and cost then you pretty much need to find a way to leverage object storage.