The real motivation for the efficiency-impairing simplifications is none of size, cost or complexity. It is to reduce replication time.
I’m not convinced that simplicity does imply reduced replication time.
Lets suppose that all the parts of the autofac require a similar manufacturing time per weight.
Lets suppose that 10% of the weight is in screws.
Imagine 20 autofacs. You might as well assign 2 of these autofacs to just manufacture screws. (Assuming they are all nearby so transport costs are low.)
Now suppose you have a screwfac. A device which has the cost and weight of one autofac, but due to economies of specialization, has the screw output of 2 autofacs.
I just scale it down by a factor of 5, and thereby reduce the duplication time by a factor of 5. So it duplicates in 5 weeks instead of 25 weeks.
This is a benefit of smaller sizes. Small, not simple.
I’m not convinced that simplicity does imply reduced replication time.
Lets suppose that all the parts of the autofac require a similar manufacturing time per weight.
Lets suppose that 10% of the weight is in screws.
Imagine 20 autofacs. You might as well assign 2 of these autofacs to just manufacture screws. (Assuming they are all nearby so transport costs are low.)
Now suppose you have a screwfac. A device which has the cost and weight of one autofac, but due to economies of specialization, has the screw output of 2 autofacs.
This is a benefit of smaller sizes. Small, not simple.