First is where the click comes from. Chances are that if your page is viewed and ads are clicked on in the USA, the click value will be much higher than if the click is in Malaysia. In fact, the same ads won’t even be seen. American ads are seen in the USA, Malaysian ads for the same keyword are seen in Malaysia. Because the competition for the same word is generally less in Malaysia, the cost and therefore, the payrate is far less.

The same thing can also be said for within the USA as well. A page about NY that is seen in NY may generate different ads and different payrates than the same page seen in TX. The chances of conversion are much higher, so therefore are the costs to the advertiser, the revenue to Google, and the payrate to the AdSense publisher.

The second factor is what ads are showing and what budgets are now in play. An advertiser offering $10/click might have their budget exhausted for the day or in an attempt to spread out their budget, their ad might not show up on a given impression. That means that the NEXT lowest available ad shows up on top. Sometimes, merchants will also just put campaigns on hold or eliminate them altogether. This causes wild fluctuations, especially in niche markets where there might only be a few players.