You may be wondering, "Code review process? Isn't that obvious?" But code reviews are pervasive. Any developer is likely to be asked at any time to review someone else's code. And you can be sure your code is reviewed. For some developers, code reviews take up a portion of each day. So there is your answer: large numbers of very well-compensated people spend a great deal of time on this activity, meaning the aggregate costs are substantial. If you're talking about a development shop the size of, say, Microsoft ... well, then, the investment regularly made in code reviews can amount to something quite impressive indeed.
That is only one of the reasons that Jacek Czerwonka and his Tools for Software Engineers (TSE) team at Microsoft set out to study how the code-review process plays out across the company. Another reason had to do with taking on a challenge they found interesting in the sense that, beyond their important role in software engineering integration, code reviews involve some rather complex social dynamics that elude simple modeling.