Right, but how many people know they're only going to be in a city for two years? Most people intend to be in a place long-term; moving is in and of itself relatively expensive (even more so the further you move) and tends to be avoided unless there's good reason to do so or unless there's no other option.
And bringing things back to AWS pricing: yeah, at first you might not know exactly what you need capacity-wise, but at some point (assuming you're actually measuring resource usage) you start to get a feel for what you need day-to-day and where things are trending. Much like with living arrangements, infrastructure hosting tends to have at least some pieces that you know you're gonna need long-term.
The more compelling reason to go with IaaS/PaaS is the convenience of not needing to run your own servers in your own rack - and it's that convenience that you're paying for, at a premium compared to hiring sysadmins. For a lot of businesses that's cost-effective, because they don't have/need enough infra to keep a sysadmin busy, but at some point that flips.
And bringing things back to AWS pricing: yeah, at first you might not know exactly what you need capacity-wise, but at some point (assuming you're actually measuring resource usage) you start to get a feel for what you need day-to-day and where things are trending. Much like with living arrangements, infrastructure hosting tends to have at least some pieces that you know you're gonna need long-term.
The more compelling reason to go with IaaS/PaaS is the convenience of not needing to run your own servers in your own rack - and it's that convenience that you're paying for, at a premium compared to hiring sysadmins. For a lot of businesses that's cost-effective, because they don't have/need enough infra to keep a sysadmin busy, but at some point that flips.