Waiting for check-in to complete and tests to pass on a Continuous Integration environment is wasted time and money. CI build can take seconds, minutes or even hours. The longer a build takes, the less frequently developers are willing to check-in their results. It is the return of the "It works on my machine" approach. The chance for conflicts and for integration challenges is increasing, their resolution is another opportunity to waste time and money.
For unknown reasons no-one usually cares about the performance of a CI build. In contrary: we usually get the slowest machine available as CI server what makes the CI-experience even worse.
How to really save money?
The calculation is simple: If 10 developers have to wait 0.5h a day for the CI to build, 5h a day are wasted. An investment of a 8 core I7 machine with > 16GB of RAM and a RAID 0 array of fastest available SSDs should amortize in a week.
Pro-active profiling and tuning of a Continuous Integration environment saves even more money. Every second spent to wait for a feedback from a CI is wasted time.
In a midrange project even a dedicated person who just cares about build performance should easily pay off.
The idea of saving money on CI hardware / infrastructure is even more mystical to me, than attempting to be extensible with Impls :-).
NEW 2016: Java EE 7 Workshops: Bootstrap, Effective, Architectures, April, 4th-6th, Munich's Airport
On demand workshops: Java EE 7 Bootstrap, Effective Java EE 7 and NEW: Java EE 7 Testing are available for streaming