With AWS you only pay for what you use or reserve.. There is no minimum fee. You can estimate you billing using the AWS Simple Monthly Calculator. Pricing is based on region and prices do vary according to region. In most cases AWS collects sales tax but it does vary according to region.
On-Demand Instances let you pay for compute capacity by the hour with no long-term commitments. This frees you from the costs and complexities of planning, purchasing, and maintaining hardware and transforms what are commonly large fixed costs into much smaller variable costs.
Reserved Instance Volume Discounts
When you have purchased a sufficient number of Reserved Instances in an AWS Region, you will automatically receive discounts on your upfront fees and usage fees for future purchases of Reserved Instances in that AWS Region. Reserved Instance Tiers are determined based on the total list price (non-discounted price) of upfront fees for the active Reserved Instances you have per AWS Region. It is important to note that Reserved Instance Tiers do not apply to Reserved Instances purchased from the Reserved Instance Marketplace.
Spot Instances enable you to bid for unused Amazon EC2 capacity. Instances are charged the Spot Price, which is set by Amazon EC2 and fluctuates periodically depending on the supply of and demand for Spot Instance capacity. To use Spot Instances, you place a Spot Instance request, specifying the instance type, the Availability Zone desired, the number of Spot Instances you want to run, and the maximum price you are willing to pay per instance hour. To determine how that maximum price compares to past Spot Prices, the Spot Price history is available via the Amazon EC2 API and the AWS Management Console. If your maximum price bid exceeds the current Spot Price, your request is fulfilled and your instances will run until either you choose to terminate them or the Spot Price increases above your maximum price (whichever is sooner).
The pricing below is based on data transferred "in" to and "out" of Amazon EC2. Note : Data transfer "in" to AWS is generally Free !
EBS-optimized instances enable EC2 instances to fully use the IOPS provisioned on an EBS volume. EBS-optimized instances deliver dedicated throughput between Amazon EC2 and Amazon EBS, with options between 500 and 2,000 Megabits per second (Mbps) depending on the instance type used. The dedicated throughput minimizes contention between Amazon EBS I/O and other traffic from your EC2 instance, providing the best performance for your EBS volumes. EBS-optimized instances are designed for use with both Standard and Provisioned IOPS Amazon EBS volumes. When attached to EBS-optimized instances, Provisioned IOPS volumes can achieve single digit millisecond latencies and are designed to deliver within 10% of the provisioned IOPS performance 99.9% of the time. Pricing for supported instance types is listed below.
Amazon Elastic Block Store
Provisioned IOPS is charged by the amount you provision in IOPS (input/output operations per second) X the percentage of days you provision for the month. For example, if you provision a volume with 1000 IOPS, and keep this volume for 15 days in a 30 day month, then in a Region that charges $0.10 per provisioned IOPS-month, you would be charged $50 for the IOPS that you provision ($0.10 per provisioned IOPS-month * 1000 IOPS provisioned * 15 days/30)
Elastic IP Addresses
You can have one Elastic IP (EIP) address associated with a running instance at no charge. If you associate additional EIPs with that instance, you will be charged for each additional EIP associated with that instance per hour on a pro rata basis. Additional EIPs are only available in Amazon VPC.
To ensure efficient use of Elastic IP addresses, we impose a small hourly charge when these IP addresses are not associated with a running instance or when they are associated with a stopped instance or unattached network interface.
Detailed Monitoring for Amazon EC2 is charged at standard Amazon CloudWatch rates of $0.50 per metric per month. Each instance includes seven metrics for total charges of $3.50 per month. Partial months are charged on an hourly pro rata basis, at approximately $0.005/instance-hour.
Auto Scaling is enabled by Amazon CloudWatch and carries no additional fees. Each instance launched by Auto Scaling is automatically enabled for monitoring and the applicable Amazon Cloudwatch charges will be applied.
Elastic Load Balancing
Load balancing is charged by the hour and by the amount GB of Data processed.
For all the current pricing details visit http://aws.amazon.com/ec2/pricing/