When using a Shopping Ads agency, the customer has 2 costs:
Paying the platform for every time a user clicks your ads. When this happens, you are charged a cost per click (CPC) by the platform provider, such as Google, Bing or Facebook. The budget a customer assigns for clicks is commonly called a ‘click budget’ and is decided by the customer how much they wish to spend. Usually, the more you spend on clicks, the greater financial returns you can expect. So it all depends on your objectives and how much you are happy to spend. (Keep in mind like any marketing method, there are no guarantees).
The 2nd group of costs is the management fee paid to the agency for maximising your campaign and financial returns. Just like many investors use investment managers for maximising profits, many companies use PPC companies for the same purpose.