Good point. I did not know exactly how much fruit pickers make, I supposed it was not very much. According to Google, the California average is 24 k USD a year, 11.49 USD an hour.
However.
A human must rest after, say, 12 hours, but a robot can just keep going even at night, if the battery charging is swift and smart (e.g. hotswap battery). So a robot could work almost 24 h shifts instead of 12 h shifts. So we get a 2x multiplier here.
A robot can be made to work perhaps twice as fast somehow, maybe it just moves faster or has four arms or can carry more or reach higher faster or whatever. So let's add another 2x.
Now we're at 4x, a single robot doing the job of 4 workers. Now we're at ca. 46 USD an hour for the equivalent of the robot's work.
Would such a robot be hired for, say, 30 USD an hour?
Next, I'll put on an MBA hat (which I don't have) and just pull numbers ouf of thin air; GIGO warning is in effect. Real MBAs please excuse the amateur hour.
Assuming the robot rental shop can keep utilization at 80% and sell it non-stop for a month to orchards, this would be 0.8 * 30 * 24 * 30 = ca. 17000 USD a month for such a robot. Let's say they spend roughly 10% in repairs etc., that leaves about 15 k USD a month. If the robot costs 150 k USD, and it can do fruit picking for ca. 6 months in a year, the robot has paid for itself after ca. two years.
My point was that the fruit orchard pays 30 USD instead of 46 USD for the "same" job (i.e. they get 35% off labor costs).
Also, a robot rental shop in this model actually starts to make profit per robot after two years. This is not such a long time, and the robots might actually become tools like tractors or harvesters are, with similar ownership arrangements, e.g. a farm co-op owns the robots and distributes to members for cheap hourly price.
Although there were many assumptions regarding the numbers, I would not quite agree on robots taking a long time to become economical. Also, the savings at the orchard side would be seen immediately, creating robot demand on that side.
Edit: typo and formatting