I have worked with audio transcriptions and data entry from handwritten notes saved as image files as a research scientist, and have a typing speed of 79 wpm. Transcribing is more time-consuming than most forms of data entry, because of the need to rewind an audio tape or decipher difficult to read handwritten notes, so I charge by the word count rather than by the hour (at 0.5-1 cent per word, depending on the project size and budget). This includes proofreading of the transcript for clarity and correctness (sometimes called data cleaning).
Some transcription jobs involve faithfully recording grammatically incorrect statements for research purposes, while others require modifying the transcript for ease of reading (reproducing some sentence fragments but ensuring the document flows well and that it can be understood at a glance). The latter is more time-consuming, but I do not charge an additional fee for this service, I only require that it pay at least 1 cent per word. If you are unsure whether your recording is within a certain budget (because you don't have a word count), it is difficult to estimate because of variable speaking speeds, but measuring the number of words in a representative 5 minute interval of your recording and extrapolating to the duration of the audio file would be an acceptable estimate, and I would consider the agreed upon cost of work binding. Please bear in mind that in long interviews, sometimes a speaker's talking speed picks up later in a transcript (what begins as a low number of words per minute turns out to be unrepresentative, because the speaker's words began to flow more quickly later). For this reason, when transcribing long interviews an estimate of the number of words in the audio recording can more accurately be taken from a middle section of the audio file than from the first five minutes.
If the transcript is to be taken from handwritten notes copied as image files or in a pdf, please estimate the wor