I'm more excited for Robot pruners. You only pick for a few days at harvest. Pruning is a year-round endeavor that is too expensive for most farmers, but something many gardeners do for best results.
You make very good points, but this is still very exciting. As you already know and most gardeners know, there are many steps in plant care that are just too expensive for human beings, but an automated system could handle nicely. The first that comes to mind is pest and weed control. Look at Carbon Robotic's LaserWeeder. I have never used it personally, but I am excited to see lasers and machinery replace herbicides and round up. Not only will it lower the cost and increase the productivity of organic food, but it is just so much more effective. Now imagine that applied to pests.
Additionally, what if we perfect a laser pruner? Instead of using a pair of snips that can transmit bacteria, a controlled laser (with a backstop) cuts old leaves, improving airflow, stopping disease, ensuring more development goes into the fruit...allowing farmers to apply the techniques passionate gardeners do to farm-scale agriculture.
You're absolutely correct that it's nearly impossible for a machine to beat a human being for picking tomatoes on a cost basis. Human beings are well adapted for picking things and most farms have short harvest windows, so you're not paying them year round. Like most innovations, I think automation will augment existing workers, not replace them...at least for several decades. However, another thing to consider is that the USA is spoiled by cheap imported labor. Some countries don't have such luxuries. Labor costs are higher in other parts of the world, so maybe this will make sense for them much sooner.