That's very tricky thing to quantify, especially with "unsung heroes". If my work is in preventing problems, the guy that fixes problems will be seen as the one that contributes more to profit, since impact is directly observed/measured.

This is something that one of the orgs I worked for eventually realized. The people f'ing up, and then fixing their mistakes, were the ones getting promotions/bonuses/raises, because they were the ones interacting with all the execs.