Recently I was reading the PLM World e-Newsletter and saw this nice table reflecting the Total Cost of Ownership (TCO).
Microsoft SQL Server 2008 Benefit over Oracle Database 11g
24 percent lower IT labor costs
44 percent lower software costs
Up to 38 percent lower cost
It was interesting that they qualified this with a comparison of SQL and Oracle both running on Windows Server,and found that the hardware cost difference was negligible. This latter item did not surprise me but does run contrary to some popular beliefs about Windows and Unix. It was nice to see a study on providing factual information in the IT community.