This guy says that using Subversion and Cruisecontrol cut their costs by 92%. It would be interesting to see how he calculated this. Regardless, it is amazing how many quality tools are available for free now.
Why Subversion Rocks
In a recent study I performed on my development groups process improvement over the past 5 years, we found that we had cut the cost of managing our build and release process by approximately 92% by incorporating Subversion and related tools like CruiseControl, ViewCVS, and other custom software (and major process changes that accompany them) to integrate and automate our release management processes.
Hopefully this response answers some of your questions.