So, if I get it right you've crossed 'adwords/adsense' with 'ebay' ? Interesting!
I'm quite curious how high the effective CPM is of your usage of screen real estate vs other advertising networks. Since the items are 'relevant' it could be quite high, but initially you might be left with more inventory than you can sell.
Shipping seems to be USA only, you may want to limit your 'ads' to the region that the seller is willing to ship to.