No disagreement, although the only zoom on the Mavic 3 is digital which can be done just as easily in post.
For a still photographer, the camera and the flight time are most relevant. The 20MP stills are the same size as those on the Mavic 3 so...
What you MEAN to say is that they have a “book value” of zero, having been totally depreciated. They can (and obviously do) have economic value if someone is willing to pay you for them. Your sale of zero book value assets will generate taxable...