Operating your business in the cloud is fundamentally different than operating on premises. And when operations differ, so too do strategies for containing costs.
Financially speaking, a datacenter requires a large capital expenditure for the building, additional capital expenditures for the servers and software licenses, and smaller but significant operating expenditures for powering the servers and cooling systems, and for maintenance and management.
In the cloud, there are no capital expenditures. Instead, there are significant operating expenditures, billed for server virtual machine instances, storage, network traffic, software licenses, and other niggling details.