Not even Bay Area prices. A Jr. SWE after overhead (benefits, HR, laptop, office-space,...etc) is easily costing the company 150k+/year in most markets.

Indeed, but take it a step further. Two ten thousand dollar servers in your basement with UPS and some rudimentary failover configuration is basically fire and forget. Remote in monthly and install updates. Done.

It'll run for ten years for next to nothing.

Until there's a power outage, flooding, malice, etc.

I think the main issue is that the cloud providers don't publish much about outages that don't affect the end-user. I mean a failed hard drive happens all the time, but S3 is never affected by that.

Depends on your bandwidth requirements. Also, if you want even higher reliability, you might consider getting two independent internet links into your basement, which is pretty doable in an urban setting.

But they wont have diverse routing :-) all it takes is a navvy with a back hoe digging in the wrong place.

And you also need to have diverse routing for power coming in and generator / battery room set up.

Run the backup from your friend's basement in the next town over using a different ISP. You can run the backup for them.

For a long time, my off-site backup was at my grandmother's house because it was the furthest geographic location I could give someone a box who would leave it plugged into their Internet. ;)