Microsoft SQL Server 2008 License and Editions

Enterprise Edition

Business Critical,Large Scale
Option 1: $24k per processor
Option 2: $9k per server with $160 per Client Access License

A comprehensive data management and business intelligence platform providing enterprise class scalability, high availability and security for running business critical applications

Standard Edition

Departmental,Small/Med Scale
Option 1: $6k per processor
Option 2: $1k per server with $160 per Client Access License

A complete data management and business intelligence platform providing best in class ease of use and manageability for running departmental applications

Workgroup Edition

Branch,Small Scale
Option 1: $4k per processor
Option 2: $740 per server with 5 free CALs

A reliable data management and reporting platform providing secure, remote synchronization and management capabilities for running branch applications

Express

Entry-Level,Learning
Free (Require a CAL to connect to paid SKUs)

A free edition of SQL Server ideal for learning and building desktop and small server applications and for re-distribution by ISVs

Compact

Client Embedded
Free (Require a CAL to connect to paid SKUs)

A free, SQL Server embedded database ideal for building stand-alone and occasionally connected applications for mobile devices, desktops & web clients

Web

Low-end Hosting
$25 per processor per month
(SPLA only license)

A low-TCO, SPLA only option for web hosters, providing scalability & manageability capabilities for shared web hosting scenarios

Developer

Development & Testing
Free (through MSDN subscription) or $50 Retail

Development only license. No production serving.

http://www.infoq.com/news/2008/07/Sql08ReleasePricing