My fees are calculated differently depending on the task. I usually use project fees for translation and adaptation work; in these cases, the fee is agreed at the start of the project.
For copywriting, editing, proofreading, and more complex adaptation work I charge an hourly fee in the three-figure range. I provide a quote with an estimate of the number of hours I expect the project to take. Should the project look like it might take longer, I inform the client immediately so we can modify our strategy accordingly. It’s also possible to agree an upper limit in advance. I prefer to estimate slightly on the high side, so we can avoid any nasty surprises.