AWS is ridiculously expensively at their scale, both for storage and egress. But the choice is not only between that and building a staffed on-premise storage facility.

You can compromise at a middle ground - rent a bunch of VPS/managed servers and let the hosting companies deal with all the nastiness of managing physical hardware and CAPEX. Cost around $1.6-2/TB/month (e.g. Hetzner's SX) for raw non-redundant storage, an order of magnitude better than AWS. Comes with far more reasonably priced bandwidth too.

Build some error correction on top using one of the many open-source distributed filesystems out there or perhaps an in-house software solution (reed-solomon isn't exactly rocket science). And for some 30+% overhead, depending on workload (you can have very low overload if you have few reads or very relaxed latency requirements), you should have a decently fault tolerant distributed storage at a fraction of AWS costs.