Which edition (Workgroup, Standard, Enterprise)?
What licensing model (per client or per Processor)?
Do you have a Select Agreement with Microsoft and if so, do you have SA (Software Assurance) on your SQL2000 licenses? How about Open Licensing?
All these factors can radicaly alter the outcome of the pricing.
Amazon.com has some fairly standard retail pricing, but there are a lot of cheaper alternatives depending upon your requirements.
AucklandSQL User Group
Independent SQL Server Consultant
SQL Server MVP