I dont think the problem is with the PID. Its mainly with the website, the content and the ads. At times the ad placement also matters. The site is not getting targetted traffic in relation to the niche and geographically also. Try PPC(Pay Per Click) dont bid on high keywords try small and test. Try getting traffic from the locations it should be getting traffic from for example eBay.com should get traffic from US if you are looking for conversion. Mostly product information page works rather than banner ads. Do a little experiment on the website/blog by making small changes and see if that brings conversion. Hope this helps. Cheers.