As my clans ship-builder, I respectfully disagree. Player-built ships already have the appeal of being way higher quality and being able to be custom-built to suit a players specific needs, The material cost vs. having 5 durability is already a little too "casual" for this kind of game IMO.
I see your point but I think we should be looking in the other direction, for example - lowering the durability on NPC ships to 3, while keeping the player built ones at 5.