It seems he wasn't able to see some of the sources. One cost money to see, one is out of print and not available...
It may be true and noble that since he isn't able to verify the data himself, he shouldn't have used it. But if you can't see the sources, you also can't state that the data is incorrect. One of those books he couldn't find might contain the data that directly corroborates this.
I suspect the cost of fixing defects has more to do with your internal process, and less to do with how much work it takes to find and fix the actual defect. I have a client I work for now for which I need about 10 days lead time to get code from development to production. So it might take 1 hour to fix a bug that is discovered, and 8 hours to do the paperwork and go through the formal process of moving code through testing, staging and finally to production.
It may be true and noble that since he isn't able to verify the data himself, he shouldn't have used it. But if you can't see the sources, you also can't state that the data is incorrect. One of those books he couldn't find might contain the data that directly corroborates this.
I suspect the cost of fixing defects has more to do with your internal process, and less to do with how much work it takes to find and fix the actual defect. I have a client I work for now for which I need about 10 days lead time to get code from development to production. So it might take 1 hour to fix a bug that is discovered, and 8 hours to do the paperwork and go through the formal process of moving code through testing, staging and finally to production.