Cloud computing has different cost models:
Pay-as-you-go
A commitment consumption-based plan
Free, on demand, reserved capacity, spot capacity dedicated
Amazon EC2 calls virtual machine capacity that is reserved but not yet used Reserved Instances. Customers who bought a reservation but did not use all of it can sell it to other customers in the Amazon EC2 Reserved Instance Marketplace.
When customers choose the pay-as-you-go model, they pay only what they consume. A virtual machine that is switched off is not billed for processing. However, the virtual machine still has storage allocated, so billing for storage will continue while the virtual machine is switched off.
Pay-as-you-go is unpredictable for cloud service providers. They cannot predict how much revenue they will make exactly. They also do not have a good estimate on the number of resources they have to allocate.
So an alternative is a plan. In this model, the customer pays in advance and commits to consuming...