This question interests me for a while.
At one extreme, I found papers, and some thesis that were outcome of change of a single parameter in a CFD code, like in the case of "Atmospheric boundary layer" turbulence model, that was produced by a single change in $c_\mu$ constant of the $k-\epsilon$ model.
On the other end there are papers, made after whole library of hundred thousand or more lines of code have been written, as in the case of big libraries like deal-II.
I find this important for understanding what is actual effort invested in writting a single sci comp paper, and to understand what this effort is consisted of.
As one approach for finding some answers I am considering to send questionaries to authors of a number of papers, and maybe plot a correlation between approximate number of code lines written and citation of the paper. This result can be published in figshare for curious ones.
I would like to hear some troughts.