For testing performance of new Google Referral 2.0 ads (on CPA basis), last week I added one CPA Ad on a page. That page has low traffic and only get aprox 10 clicks till now with no conversions. I'm not sure if has any relation, but now my CPC average has decreased aprox by 15%. I've read that low conversion rates on CPC sites (those paying the CPC ads) could be the cause to be smart-priced. Maybe your own low CPA conversion rate could cause to be smart-priced too ? Has anybody noted any relation betwing CPA conversion rate and CPC prices ?
Have you read that on adsense.blogspot.com ? or through AdSense Support ?, or maybe you're simply guessing ?
It would be really dull if they did using smart pricing on it as you could just have on CPA offer that pays very well, but is much harder to convert than the rest.