There's also one argument which your CTO didn't make, but really should have: Hetzner is less reliable. For instance, both my postgres master and replica went

There's also one argument which your CTO didn't make, but really should have: Hetzner is less reliable. For instance, both my postgres master and replica went down one day the other weekend, because another machine in the same rack popped the breaker. In my specific application, I can cope with a once-in-a-blue-moon blip like that -- Hetzner saves me literally thousands of dollars per month in compute and bandwidth, I like doing [a limited amount of] sysadmin, and it's worth the trade-off. But, how do you think your CTO is going to feel about this move when all of your dev VMs go down just before a big customer deployment?