Every few months of this spend is like buying a server
Edit: back at my pc and checked, relevant bare metal is ~$500/m, amortized:
https://baremetalsavings.com/c/LtxKMNj
Edit 2: for 100tb..
we're using Filestore out of convenience right now, but actively exploring alternatives.
If you run a single-digit number of servers and replace them every 5 years you will probably never get a hardware failure. If you're unlucky and it still happens get someone to diagnose what's wrong, ship replacement parts to the data center and pay their tech to install them in your server.
Bare metal at scale is difficult. A small number of bare metal servers is easy. If your needs are average enough you can even just rent them so you don't have capital costs and aren't responsible for fixing hardware issues.
Some things that are hidden in the cloud providers cost are redundant networking, redundant internet connection, redundant disks.
Likely still cheaper than the cloud obviously but you will need to stomach down time for that stuff if something breaks.
All of that costs money and time. You're probably better off using cloud hosting and focusing on your unique offering than having that expertise and coordination in house.