One of my longest contracts was being on call for a a company to assist with their cloud setup. Most of this is
not abstracted away all that well. Having managed both on premises, colocated, managed servers and cloud services, my customers when I was consulting tended to need
more of my time for similar sized setups to manage cloud setups. Yes, with a colocated setup we needed to rack and wire up servers, but the amount of time spent for the lifetime of a server was typically measured in single digit number of hours amortised over several years.
EDIT: As to why the time to manage colocated servers is so low, consider that pretty much everything has IPMI or similar now, so apart from a few hours setting up an initial provisioning server for the entire environment, on a per server basis you're connecting power, screwing on rails, connecting the network, configuring IPMI (remote reboot, remote KVM, remote sensor access), running your provisioning scripts and starting (automated) burn-in tests, and then you have a bunch of new capacity in your orchestrator at the end of it. Everything else is pretty much the same as using a cloud provider, except your instance sizes are tailored to your actual workloads. The odd replacement of broken equipment can often be handled by your colo provider. When I was racking equipment myself, I'd often install more than one server an hour, and then not touch that server again physically for several years. Monitoring is largely the same - you need to be able to migrate away from failing instances either way, only now some of those failures might mean hardware has failed and you have a few more indicators in your monitoring system matching your IPMI sensors.