I say this simply because some of the drops out there are just immensely stupid to get.
Case in point: Trojan Horseshoe. Drops off? Those Horse Knights. How often do you see them per floor? Per run?
The /ONLY/ good place to farm these are Tier 3, in the latter half after the terminal. Okay, that's fine, hard enemy... hard part of a dungeon.
Except that the drop rate is low. Extremely low. It's a 4-star item so I understand it not coming off of every knight I see, but the fact that I don't see any knights in most dungeons is just ridiculous. And even then, it's maybe 1 per floor.
Rare drop + Rare monster? Okay, that wouldn't as much of a problem if you only needed say one per recipe.
But wait: Mad Bomber Suit (as an example) needs TWO. TWO HORSESHOES.
Now this wouldn't be as bad of a problem if you could trade tokens in for-- oh wait. You can't. YOU CAN ONLY GET THEM AS A DROP.
Needless to say, there seems to be some sort of glaring problem (at least to me), when ONE component of an item is worth more than the item's recipe itself, the other mats, and the energy and crown cost. Seriously.
There aren't many truly rare materials in this game. I'm pursuing the bomber armor myself, so I'm going to need horseshoes, but I'm ok with the fact that it's going to be really hard to get them. It gives me a goal to pursue that I can't complete in a day or possibly even in a week or month. I like playing the game and pursuing specific goals makes it even more fun. If I run out of goals too quickly, it won't be as much fun, so I say keep the horseshoes rare. People can wear other armor while they try to win them.