So I had a crafting system in place. And then it didn’t work.
The problem was that the value of ingredients for magic items would become ridiculously high. This would encourage selling them, or deciding to spend a few months just gathering precious ingredients and then, I don’t know, buy an army.
In other words, it would break down the game.
An obvious fix would be to just increase the number of ingredients that’s necessary for an item. This way, they would all become less valuable. I thought about this, but I don’t like it as a solution. This is because if the ingredient count increases too much, the system discourages players to just gather materials during adventures and instead prompts them to claim downtime and gather a lot of resources. Which would be strategic, but not a lot of fun.
So something else needs to happen.
One way would be to put a skill check after the resource gathering part. A rare, powerful magical item would set a high crafting DC and so even gathering the ingredients would not be enough, as the crafter would need good tools, proficiency and maybe some special advantage to succesfully create the expensive item. The key thought here is that the crafting itself adds value and that constituent items would not necessarily be valuable.
Another is to say that magical items need magical ingredients that a player is unlikely to gather, except if the DM deems it reasonable to hand it out. Patching that onto the existing roll table would probably mean that after rolling an ‘aethereal’ resource, an additional roll would need to ascertain whether the resource is actually magical. If the players however have performed some appopriate actions (kill a magical beast, steal the core of the magical flying castle, mine the depths of the Underdark), such rolls won’t be necessary – it’s just during the foraging type gathering that the odds of finding such a resource are so slim.
And a third option is to use both. I am going to go for both and see where that gets me.