It wasn't my intention to claim that it could be calculated exactly. It was my intention to point out the distinction between software engineers, where there's a bottom line somewhere to be counted, and teachers, where the bottom line is effectively impossible to calculate.

This isn't about how much programmers are worth, but about why it is we get away with paying teachers so little while programmers are paid so much: their contribution to a corporate profit. The details are beyond the scope of the post.