There's options outside SaaS object storage though, eg running your own MinIO or Ceph, + DAS (or SAN) at your colo. Yes it's some hassle but if you have significant expenses from SaaS it might be worth checking out.
AWS S3 buckets have a limit of 5gb/s access to a single bucket.
Unless that limitation has changed in the last couple of years; I can easily make a system beat that, if that's the requirement.. and ultimately it does come down to understanding requirements. :\
I think generally people forget that cloud is just computers too, it's really not anything special, and amazon/google/microsoft are solving the general case (and, doing so well, actually) but this comes at a high premium.
It's 25Gbps now[1]. I have a rule of thumb: if I haven't refreshed something I think I know about AWS for more than half a year, it's probably out of date.
25Gbps is 250 cable Internet users downloading the release of your new software. What you call a DDOS is actually a woefully underwhelming instantaneous transfer rate.
Lots of providers claim to offer object storage, but try hitting them from couple thousand cores and they all tend to immediately fall over.