Huh. Maybe I'm just too early in the game still (despite having put 10+ hours into it) but crafting materials are like, the one thing I'm not hurting for. It's got the Zelda rupee problem for me, at least at this point in the game -- I'm constantly pegged at the max capacity, and it feels like I have basically nothing to use it on. (I mean, I do use the tools I have found so far, situationally, but I don't think I've been down by more than ~100 or so from max other than for that one wish in the starting area.)
Edit: Ok, I'm a bit further in now, and I see what people mean... -.-