What is the difference between a marketing retainer and project pricing?
A retainer is a recurring monthly fee for ongoing work, usually with a defined scope of activity rather than a defined endpoint. Project pricing is a fixed fee for a defined deliverable with a completion date. The distinction that matters is whether the work has a natural end. Retainers suit continuous work and can drift into paying for presence rather than output; projects suit finite work and can leave you without support once delivered.
Agencies prefer retainers for obvious reasons: predictable revenue, longer relationships, easier planning. That preference is legitimate but it is not always aligned with what you need, and the misalignment shows up as a monthly invoice for a task that was completed in month two.
The useful question is not which model is fairer. It is whether the work you are buying actually continues. Some does, genuinely and permanently. Some does not, and the honest answer is a project fee and then leaving you alone.