Tbh I think full automation is different from productive forces development. Let’s say we get a robot R which can build itself. So R=2R=4R etc, each robot after the first one would have zero human labor in itself, so it’s labor value is 0. Considering we would get infinity of this greygoo-like robots their exchange value should be zero as well. However, on the other hand, the first robot is a product of labor, let’s say 1000000 human hours. We can estimate subsequent labour values as 1000000/(number of robots).

How capital would deal with such a scenario? Look no further than software, its first creation is labor intensive, but the copies of it are practically free from labor. So low-copy software costs a shitton, while popular software is cheap.

So, in capitalism automation likely would perpetuate rent extraction in some form, even if robots are dirt cheap. In centrally planned economy robots would be created to reduce socially needed labor hours, I guess.