Why does Amazon have ads?

What CPM does Amazon charge for its display ads?

• Amazons display ads program - http://www.amazon.com/gp/feature.html?ie=UTF8&docId=1000347381 - can be used by advertisers to show ads on http://amazon.com. What is the typical CPM that amazon charges ?

• Answer:

  I think it is possible to make a fairly good guess that the CPM is equal to or less than typical rates that Google charges, for the simple reason that Amazon offers $75 of free clicks as a trial offer, whereas Google offers $100.  This suggests to me that a) they are aiming for the same market b) Amazon expects to deliver a number of clicks that compares respectably with their leading competitor.  I also would expect CPM to be lower because Amazon's advertiser-funds-extraction-algorithms must be less efficient than Google's, which are both more mature and better resourced as ad revenue is 97% of Google's revenue rather than 1% or less of Amazon's. [UPDATE]: however, it has since occurred to me that Amazon's CPM might be helped by the different composition of its demographic ... its users are already shopping, which is arguably further along than Google's users, who are searching preparatory to shopping (this is painting with a very broad brush. I hope someone comes along with a more empirical answer for this question.