A 4U or 8U rack server with 1 PB of storage and plenty of cores: ~$40K
Colo facilities in the Bay Area: $400-500/mo
Compared against the status quo of $9K/mo, the ROI ends up being 5 months per box, for twice the storage capacity they need. Set up multiple of those boxes around the world to the extent that you care about redundancy/distribution, and they still end up far ahead in a few years time.
The machine also needs to be replaced every $interval. After 4 or 5 years, keep it up is more hassle that replacing it.
A single machine patches and will need to reboot. What should happen to people trying to access the store?
Keep replicas help, ensuring a petabyte or even half a petabyte of small files is in sync across multiple sites with various link speeds is not as trivial as rsync.
A half petabyte at other places such as wasabi would cost 35k a year, including bandwidth.
Open street maps by comparison in 196GB compressed including full history. 20 years of full snapshots would amount to only .2PB, or 20k a month to host on cheaper storage providers.
I don't think using OSM's budget was the best example.
And if any downtime for upgrades is unacceptable one can go for distributed storage solutions like ceph, seaweedfs or minio. Or simply 1:1 mirror everything to a second machine (which you want for disaster recovery anyway) and switch over during the maintenance period. And since for this specific usecase the server(s) would only serve as CDN origin, a brief downtime might even have very little actual impact.