If you are preparing audio for a transcription service, there are several things you can to do reduce the length of time and overall cost. Consider the length of the video, the number of speakers and the technical subject. Plan these out when you are setting up your initial recording.
Even more importantly, make sure the audio is clear. If possible, minimize noise and clipping when recording. Be sure to test microphones ahead of time. Use a lavalier microphone attached to the collar of the speaker instead of a microphone several metres away. Have a professional monitor the initial audio. This will ensure that the words come out audibly and clearly.
Avoid outdoor recording in places with loud ambient noises like cars, dogs barking or an airport. A directional microphone or lavalier mic can reduce unwanted noise. Inaudible recordings can contribute substantially to the length of time of transcription as the transcriber will have to replay sections often and still may not be able to decipher what is being said.
Where appropriate, ask participants to repeat themselves if you feel they were not clear or loud enough. Or ask them at the outset of the recording to speak loud and clear.
A good transcript will take several hours to produce. Even though it may seem like a long time, the reality is that in the end you will have a professional transcript that represents well what you took the time to record.