Photo by extranoiseThe QCP algorithm uses a combination of metrics to assess the EPC that you will be paid for the traffic you have driven. In addition to looking at the revenue driven by yesterday’s traffic, it also takes into account historical information, such as the long term value of the users that you bring to eBay and the value from sales that happened within the 7 day cookie latency. Therefore, the EPC is comprised of more than just the sales and ACRUs you brought in on any single day.
EPCs will move up or down over time. The more revenue you bring for a certain number of clicks, the higher your EPC will be over time. Less revenue for a certain number of clicks will result in lower EPC. In some cases the full commissions from a sale may not be reflected in your EPC that day. Instead it will serve to increase your overall EPC.
In addition to this, if you increase the number of clicks you are driving to eBay or started a new campaign, then your EPC is likely to fluctuate more than normal as you build up a history. This is because eBay uses revenue generated very close to the click as a way to calculate the value of the new campaign or increased volume of clicks.