Our friends over at Spyfu.com have a formula for estimating how much any website spends on Google Adwords advertising each day. Penny Auction Insider ran all of the known penny auction sites through Spyfu and created the following graph of the eight that spend the most on Adwords. Bidcactus and Swoopo spend by far the most, followed by BidsTick, no other penny auction site spends nearly as much on Adwords.
Please note that Spyfu.com stresses their data is an estimate. Also, Spyfu provides a min and max number (in blue and green, respectively), and I went in and calculated an average (in red) as a means of trying to better compare each site's numbers. Please note that taking the average makes the numbers easier to compare but may also further distort the picture.