Why is it my conversion is beter from a low value click than a high one on adwords? How can I decide which one to use to determine what level is best to set?
Assuming that you've got enough conversions to get an accurate read on the conversion rate, there are quite a few possibilities... People are clicking on the top few keywords to research a product - this is quite likely for terms like "digital cameras", but given your cpc, I'm guessing that you're bidding at specific terms. Changes made by your competitors - perhaps a sale ended, or somebody has stock issues? Seasonality. Particularly an issue with fashionable items like clothing - do people still want what you have. Pricing - are your prices as competitive as they were? Stock Issues - have you sold out of a number of lines? Personally, I'd run the test again, to be sure. If you still get the same results, go for the one that gives a better return on investment...
I am using specific terms now and have decided recently to remove some of the non-specific terms as I suspect those are the ones with the high click high cost and low conversion. I have started running the test again with the bid price for the non-specific terms reduced hopefully this could change the trend. Its quite a low number of impressions at the moment but increasing.