I could have reviews during or after unit testing without either of these problems, I would love to look at the numbers to see where the break-even point occurs. True, software is NOT like ball bearings, and each module will differ. And, if the process for requirements and design are close to defect free, then we should be able to create software which is pretty close to perfect. This is not just a facetious remark. But perhaps that is a new thread.
All defects have different costs to repair, and unknown loss of business.
However, I would profess that it would be prudent to continue to remove a requirement for peer reviews as processes prove that the human variations are being minimized by process perfection. You could measure the cost of quality in a couple of ways, but you would first need to know the cost of no quality. Then, you can actually financially justify quality programs. Simple break-even analysis of where the cost of doing quality functions begins to outweigh the cost of releasing defects would indicate when the quality program pays for itself. I am not sure what normalization would be required.