Except that ships in ST always travel at the speed of plot. Travel time has never been a remotely reliable indicator of distance. Hell, three movies later it took them less than half an hour to reach the center of the galaxy
. Even if we ignore that (yes, please, let's ignore that), in the sixth movie it doesn't take long at all for the Enterprise
to get from Earth to the Klingon border and for the arrested Kirk and McCoy to subsequently be taken to Kronos (one assumes) for trial and then shipped to Rura Penthe. So by those standards, a 3-day journey could represent a pretty significant distance.