The bottom line is these items should be obtainable for people who do a lot of playing the game, however be out of reach for players who only farm a certain area, hence I recommend needing materials from spread out monster types, and potentially even spread out status types.

Before battle sprites every material was useful. Trading 20 tokens to brinks for one 5* material was a legitimate use of the tokens. Now-a-days, materials drop like candy, and with up to x4 the materials per party that's a pretty huge number of materials swimming around.

Making an item too far out of reach means it's still a rich-only premium of a weapon. Making it too easy to get takes away the charm of the item. Making it cost an absurd but painfully doable amount is that middle I want to reach.

I guess what I want is for materials to get a proper sink, desirable gear to find its way into the system, but also give value to individual materials instead of their star levels.

A few other ideas I thought about was requiring a small handful of harder-to-acquire materials. Something like, say, 10 dark embers and 3 maiden's tears for more of the item. 30 snarbostuffing and 3 nightmare manes for another. Makes shadow lair materials more desirable, and boss token materials also pretty helpful. Throw in some mod calibrators, enamorocks, and rock salt and it becomes a more overall involvement for the item rather than just a single area.