Comparing what Nebraska spends on coaches to what Northwestern and Illinois spend is a ridiculous exercise. Where do we rank among teams that we think we are as good as? Where do we rank in both salary and years of coaching experience (at the D1 level) in comparison to Ohio State, Wisconsin (before the coaching change), Michigan, Alabama, Oklahoma, Oregon, etc.
As knapplc said, it isn't about salary. Nebraska could pay Papuchis $900,000, he's still going to be a mediocre defensive line coach (he's not the coordinator if he doesn't call the plays).