Costs are central to designing for the cloud. Selecting the most appropriate options from a wide variety of tunable parameters available for each of the services can make this a challenging task. Typically, if you understand the costing for your compute nodes and database services well, then you would have largely accounted for a big chunk of your expected bill. Using an 80:20 principle can help you get to ballpark cost estimates, quickly. Typically, if you understand the costing for your compute nodes and database services well, then you would have largely accounted for a big chunk of your expected bill.
Most cloud service providers make online calculators available to arrive at the ballpark figures for your infrastructure. The following is a sample screenshot for provisioning AWS EC2 instances (compute nodes) in a calculator provided by...