So I've been experimenting a lot with the new features of trapdoors in 1.9/1.10 (I'm a little behind the times) since they are so much more versatile now.

However, now that I'm making more of them I noticed something odd about the crafting recipe for iron trapdoors compared to wooden trapdoors and iron doors. I can't possibly be the first person to notice this, but I searched and couldn't find anyone asking this question, so here goes.

A single iron trapdoor costs 4 iron ingots, while you get 3 iron doors for 6 ingots since a few updates back, so they effectively cost only 2 ingots apiece.

Why do iron trapdoors, which are half the size of iron doors, cost twice as much to make? I feel like the recipe ought to provide two instead of just one, like wooden trapdoors.

Any thoughts?