Wouldn't the position of your ad have more to do with the way its presented on the publishers end than how much you bid?
Each publisher's presentation of Adsense ads is unique - so, some might present 1 or 2 ads... others may present 3 or 4. Based on this, position on the Content Network is incredibly important because a lower position can cut you out of distribution from sites with fewer ads shown. Unlike the search results which can include 10+ ads on page 1... and more on subsequent pages... position on the content is arguably more important than search.
