There's still the overhead cost of collecting this data and the operational cost of delivering it. Many government functions charge money because it's unsustainable if they don't.

For example in Seattle people can request body cam footage arbitrarily. But the faces and identifying info of witnesses and victims need to be redacted which takes time and money. Someone started bulk requesting almost all body cam footage, and that placed a big cost on the police department. Now they charge $17 per body cam request.