Before starting on the dealer side, I was with eBizAutos. First, as a Data Collection Specialist, with our quota (including printing stickers & driving from dealership to dealership) was no fewer than 20 vehicles captured per day. Once a routine was established, it was not difficult to get 30-50 cars shot per day, depending on difficulty in gathering keys, staging the vehicle, etc.
On the dealer side, I was limited in the time that I could dedicate to shooting cars, so I aimed for 12-15 per day. Once the inventory turnover met a certain threshold, we brought in a dedicated photographer for the task. With the... unorthodox nature of the photo booth, and vehicle prep system that was set up for her, she would get around 15 vehicles shot per day.
With a more efficient set up, I don't see why a dedicated & motivated photographer couldn't get at a bare minimum of 25-30 cars a day done. If you are adding video, that would obviously reduce the number of vehicles photographed.