Microsoft announced the pricing for SBS 2008 and EBS 2008 on May 12, 2008. In a nutshell, pricing is as shown below

Windows Small Business Server 2008 Standard Edition software, including five CALs, $1,089 (U.S.); additional CALs $77 each (U.S.)
 
Windows Small Business Server 2008 Premium Edition software, including five CALs, $1,899 (U.S.); additional CALs $189 each (U.S.)

Windows Essential Business Server 2008 Standard Edition software, including five CALs, $5,472 (U.S.); additional CALs $81 each (U.S.)
 
Windows Essential Business Server 2008 Premium Edition software, including five CALs, $7,163 (U.S.); additional CALs $195 each (U.S.)

Straight from the source, read it here

http://www.microsoft.com/presspass/press/2008/may08/05-13PublicPreviewPricingPR.mspx