I wish that I understood this post. I am upvoting you in the hopes that you feel obligated to explain further.
My understanding of the "quantity to quality conversion" phrase is that in many situations the relation between some inputs and outputs is not linear. More specifically, there are many situations where at the beginning the relation seems linear, but later at some point the increase of outputs becomes incredibly huge (incredibly = for people who based their models on extrapolating the linear relationship at the beginning). Even more specifically, you can have one input "A" that has obvious effect on "X", but almost zero effect ...
Related to: What Do We Mean By "Rationality?"
Rationality has many facets, both relatively simple and quite complex. As a result, it can often be hard to determine what aspects of rationality you should or shouldn't stress.
An extremely basic and abstract model of how rationality works might look a little something like this: