Yes, TCO can be higher, depending where you are on the curve of capex, amortization, and staffing costs. Don't forget you still need at least Developers, DevOps, and Security. If you're inefficient at cloud, spinning up ec2s left and right, using a lot of egress, storing a lot of hot/live data, your total cost is much higher, and will easily be more than the salary of that one sysadmin, or team of systems engineers, you would pay to maintain the colo space.

You have to do a lot of things right to get that Cloud Value, as the author of this blog post has shown. You have to do a lot of things right to get value out of on-prem bare metal as well, but those things are generally well-known, standardized, have less moving parts, and people with decades of experience and knowledge of best practices. The opposite of the current cloud landscape.

TCO is not a straight line.