I worked on a tool at Amazon once that incorrectly calculated royalties, not because Amazon was greedily trying to steal from publishers, but just because of general incompetence (or, lack of sufficient competence maybe). Basically, of the people who wrote the tool, tested the tool, and used the tool, none of them knew exactly how royalties should be calculated and none of them could tell whether or not they were bei…
I worked on a discount calculating service with no prior knowledge.It was supposed to replicate an existing system, so we went through the oroginal specs and general litterature to get a sense of what we were supposed to make.
First day of test with a employee in the field, and it appears that they have specific calculation rules that are so obvious to them that it didn't warrant to be written. Welp. And a few iterations after we were still hitting blocks of "what ? didn't you know that in case of X you do Y?" due to us being outside of their field.
Real world systems are hard. I'd still blame Amazon for not having caught these issues very early in the process, that's on them. But bugs and gross calculation errors are par for the course.