Cloud bandwidth costs are a rip off. For this particular situation though, make sure to replicate your files across multiple buckets, one in each GCP zone, otherwise you incur the cross zone transfer costs. We do something similar to serve julia downloads, because it turns out that most downloads are from people running on the cloud (so we basically replicate our binaries to every cloud provider and then to every region for that cloud provider). Everything else then goes through fastly for us (we also use fastly to serve custom redirects if your request comes from one of aforementioned cloud providers). That works pretty well. You do have to monitor it though to make sure that load doesn't suddenly shift to a cloud provider you didn't account for. For example, after GitHub actions became widely used, we suddenly started seeing TB/day traffic from Azure, which we hadn't deployed any caches to, so our bandwidth utilization on Fastly shot through the roof. (Side note: Shout out to fastly for hosting our binaries for free!). Without the cloud provider caching setup, we'd probably be at similar $/day costs, but this way it's basically free (even without the free fastly service, we'd only be at ~$1000/month or so).