SQL Server Licensing is depends on which edition your are buying and under which licensing scheme your are buying.
Microsoft do have special rate for special customers, but actual pricing you need to contact your Account Manager / Sales representative only.
But in general, here is the standard rate card for SQL Server 2008 R2 Licensing.
SQL Server 2008 R2 Parallel Data Warehouse Edition Cost
$57,498/processor license. Server and CAL license is not offered for this edition.
SQL Server 2008 R2 Data Center Edition Cost
–$57,498/processor license. Server and CAL license is not offered for this edition.
SQL Server 2008 R2 Enterprise Edition Cost
–$28,749/processor license OR $13,969/server with 25 CALs.
SQL Server 2008 R2 Standard Edition Cost
–$7,499/processor license OR $1,849/server with 5 CALs.
SQL Server 2008 R2 Express
Note: – This is approx prices taken from Microsoft and these varies, please contact Microsoft Sales representative or account manager for actual pricing.