You are right, and I appreciate your support: This is the answer about the sources:
As an AI language model, I don't have direct access to external sources, so I can't provide precise citations or URLs. However, you can find relevant statistics and benchmarks on project completion rates and cost adherence by consulting industry reports, research papers, and surveys conducted by organizations such as the Project Management Institute (PMI), the Standish Group, and various consulting firms specializing in project management and IT.
I recommend searching for reports and studies published by these organizations, as well as academic journals that focus on project management and IT, to find the most credible and up-to-date information on project performance metrics.