Sure, but the overall percentage paid out to publishers will be obvious whenever Google issues a quarterly report. (It was about 77% for the last quarter, by the way.)
In any case, AdSense publishers need to think like publishers, not like owners of affiliate sites. Instead of worrying about commissions, they should be tracking effective CPM and total revenues. Is the "Ads by Google" box producing enough revenue to justify the space that it takes up on the publisher's pages? If so, great. If not, it's time to say "Google-bye."