Forbes ran a story a couple of days ago that ranked which shows make the most money solely based on advertising spending estimates from TNS at the end of January. Some of the results will surprise you (and me). It has 24 leading the pack, and Heroes, Survivor, CSI, Extreme Makeover, and Worst Week (yes, that Worst Week) all ahead of House, even though House has the much better demo numbers of all of those shows (even 24!).
Based on the estimated cost per 30 second advertising spot, they came up with revenue per 30 minutes so that 30 minute shows could be easily compared.
While the article does go into some disclaiming the truth of it is you can concoct these sorts of lists with estimates any way you want, and come up with rankings. Because there is no way to quantify or validate the numbers because the networks aren't going to release any of the actual results.
Although I think it's a certainty that House is making more on advertising revenue for 30 second spots than Heroes is (or was, even on January 31), it's not really different than Jeff Zucker talking about how well NBC manages the margins. Because we'll never actually know! We won't wind up seeing any data about how well the broadcast network manages margins. You will never see anything but rough estimates since it is grouped within NBC Universal in any of GE's reporting.
I don't fault Forbes or TNS, but like horoscopes, it is the sort of thing that should probably be used for entertainment purposes only.