Maybe - I have a number of services that can tolerate a small amount of downtime if they fail, during which I would spin up a replacement AWS server. 99% of the time I'm only paying for the one machine that's running. These would all need dedicated hardware failovers if they weren't hosted in AWS (the same system does have hardware components, and they either have redundant failovers that are mostly idle, or for clusters we run at 66% capacity to allow for failure. Either way, it's often not true that one hardware instance can be substituted for one AWS instance, unless you don't care about long downtime when the hardware fails).