I once had about three racks full of servers under my control, admittedly they weren't a ton of disks, but still the hardware maintenance effort was pretty much negligible over a few years (until it all went to the cloud).

The majority of server wrangling work I spent dealing with OS updates and, most annoyingly, OpenStack. But that's something you can't escape even if you run your stuff in the cloud...

True, this is a large reason why we chose to have the datacenter a couple blocks away from the office.

Why 5h a week? Just for hardware?

a) 5hrs/week is negligible compared to that potential AWS bill.

b) The seem tolerant of failures so it's not going to be anything like 5hrs/week of physical maintenance. It will be bursty though (eg. box died, time to replace it...) but assuming they have spares of everything sitting around / already racked it shouldn't be a big deal.