This is just my guess, but I think the intention from the judges is not to actually calculate a true number. The reason they used the cost of publishing fees in the piratebay case was likely to illustrate how the court distinguished between a legal publisher vs an illegal one. The legal publisher would have bought the publishing rights, and since piratebay did not do this, the court uses those publishing fees in order to illustrate the difference.
If the court wanted to distinguish between Microsoft using their own programmers to generate code vs taking code from github users, then the salary in question would likely be that of Microsoft programmers. It would then be used to illustrate how a legal training data would look like compared to an illegal one.
If the court wanted to distinguish between Microsoft using their own programmers to generate code vs taking code from github users, then the salary in question would likely be that of Microsoft programmers. It would then be used to illustrate how a legal training data would look like compared to an illegal one.