Cost of Quality (COQ) sums four buckets: prevention costs (training, mistake-proofing), appraisal costs (inspection, testing), internal failure costs (scrap, rework), and external failure costs (warranty, recalls, lost customers).
The strategic insight is that money spent on prevention is far cheaper than money lost to failure — typically the "hidden factory" of failure costs dwarfs the visible inspection budget. COQ makes the financial case for quality improvement.