EC2 is Amazon’s cloud service for flexible use of virtual machines. One of the big advantages of this service is that Amazon’s hourly prices also include the cost for the Windows and/or SQL Server license. Amazon has just announced lower prices for Windows EC2 instances.

It’s not always easy to calculate total monthly costs for various configurations, so in this post I will try to give an indication of montly costs for configurations that would be relevant for SaaS applications with 1,000 – 50,000 customers.
Note: In the monthly prices below I have incorporated the upfront costs for 1- and 3-year contracts in the monthly prices (spread out over the full term).
All prices are calculated for the EU region (Ireland).

Windows web server. No additional storage.

Traffic out (to the internet) is an additional €92 per TB.

Load-balanced high-activity Windows web server.

Amazon Elastic Load Balancer
3 M3 double extra large EC2 instance on 3-year terms
5 TB of internet traffic per month
Total cost per month = €1763

Database server, EC2 instance with Windows server 2008/2012 and SQL Server Web Edition 2008/2012.

Prices below include 1TB of database storage on EBS (Elastic Block Storage, Amazon’s virtual drives). For instances without guaranteed I/O I have included 500 million I/O requests per months. Upfront costs have been spread over the months of the term.

Note that you would also need additional storage for database backups, which could add €100-500 per month, depending on backup methods and backup retention.