Looks like the penalty by default is 2.5% per tile after 6, so a 50% reduction doesn't extend the range without penalty, it just cuts the penalty to 1.25% per tile after 6.
I guess it works this way so that if your the Terran's and have the ability for the 50% reduction to shipyards, then get the talent for an extra 50% reduction. you get a 100% reduction meaning all planets become green no matter the distance. kinda nice if you have spread out planets or want to push all your production to the front lines. You can have a fleet of shipyards all together pumping out mega ships to make a new fleet every turn.
