So why would you pay $500 more to get a drone from them when they are obviously getting their drones from other sources (overseas) and marking them up as if they are paying some sort of tariff and passing costs along to you? Do you believe you...
I don't think Payload mode is triggered by a sensor or by flight performance. When you enable Payload mode, the behavior of the drone is recalibrated to accommodate the extra weight attached to the drone.
Since the F stop number is the ratio of the lens focal length to the diameter of the front of the lens, two cameras with exactly the same size aperture/opening will have the same "f-stop rating".
Differences in lens materials, the sensor, etc...