I have a clear British voice which is free of any strong regional accent. Thanks to many years in international situations, I have learnt to speak in a way that is understandable to many people. I have many years of training as a non-professional actor, which ensures my voice is clear and projects well. Although I am a newcomer to voiceover work in my professional life, I have the right equipment (good condenser microphone, pop filter, audio editing software) and will do a good job on this.
Producing one hour of content requires more than one hour of work, so my hourly rate is per hour of work, not per hour of content. If the conditions of the job are as you describe, with the audio pre-recorded but no transcription, then the work will involve listening to a segment, noting the text to be spoken (mentally or in writing), speaking it for a voice recording, checking if that is suitable, re-recording if necessary, and then moving on to the next segment. So I estimate 3-4 hours' work per hour of final content, perhaps a little less.