Down as well as up
Renting services from AWS or other providers makes sense if you carry out projects that might fail (such as the CEO's pet buzzword du jour concept) or have a fixed lifespan (such as migrating to new services) -- a year down the line you can simply trash the data and tell the provider the monthly contact is at an end. The alternative is to be paying for hardware and premises that you built out for a project but have little use for now (until the CEO hears a new buzzword...)