Do you use a PPC agency to manage your PPC? If you do, what metric do they use to measure their success?

Hi,

I’m considering using a PPC agency to help manage my PPC because they are more knowledgeable than me. It was interesting that they would charge by the percentage of the PPC revenue (the sales that come from PPC orders). To me, that’s not an accurate way to measure success. The increase in PPC revenue could come with the increase ACOS from aggressive bidding strategy. For me, the success should be measured by the decreasing ACOS because that shows the effectiveness of the PPC strategies. However that’s not entirely true. There are ways to configure campaign to produce lower ACOS but not many sales.

What do you think? If you’re using a PPC agency, I would like to here how do they charge and measure their success. Thank you.