I completely agree with you in its current incarnation. There is no way this is even within an order of magnitude of the price/performance ratio of a migrant farm worker (who are career farmers and much faster than you or I).
However, I suspect a device like this will scale well cost wise with longer rails, thus larger versions working in a elongated greenhouse would probably significant efficiency. Additionally, you will need a device like this if you want to do vertical hydroponic farming, as the efficiency of people drops precipitously as soon as they can no longer easily reach the plants they're working with.
Having worked in a greenhouse, much of the planting is automated in large-scale shops already through vacuum planters. Watering is similarly automated through irrigation systems.
Now, vertical hydroponics, that's one I hadn't considered. That may be a good point. I lack any experience with those systems, though, so I hesitate to comment.
However, I suspect a device like this will scale well cost wise with longer rails, thus larger versions working in a elongated greenhouse would probably significant efficiency. Additionally, you will need a device like this if you want to do vertical hydroponic farming, as the efficiency of people drops precipitously as soon as they can no longer easily reach the plants they're working with.