This varies per client and their needs. It is important to understand the difference between a retainer fee structure and an hourly rate, however. A retainer does not mean you will get unlimited hours from your PR agency. Do not expect it either. It simply means that you are purchasing a sum of hours from your account team to manage the work at hand. If you go over the budget allotment, an agency should be reporting to you and letting you know that you are about to exceed your monthly budget. This is how an agency makes its money. A $5,000 a month retainer is not the same as a $25,000 a month retainer – and agencies with good business models share this information with their clients.