"Completed Code" is a myth. Yes - I am well aware that there have been quite a few examples of some glaring examples - Wheel of Fortune is one that often comes up on that list.
Having said that, EVERY system never really meets its first "true test" until it is in the hands of a variety of users and it is turning up imperfections, bugs and the like. This applies to pinball or otherwise - i.e. Financial Systems, Sales System, EVERYTHING.
Notice that virtually every computerized device or system receives frequent code updates - if you have a smartphone and apps you see this regularly.
IDEALLY, everyone would like code to be at "Final State" the moment you are using it - but that is exceptionally rare. Until the user community is finding new ways of breaking the code or uncovering bugs or shortcomings, the code has never really been stress tested.
The Gulf that exists is between code that functions properly with most features functioning properly - and that of UNFINISHED code - which I think is the perception pinball suffers at times.
It's just my 2 cents - but I think it is a valid point of view that is relevant to this discussion.
Oh - paying for code updates - Bad Idea - for many of the reasons identified by others above me in the thread.