My game has lootboxes that give you specific items, e.g. a hat, hair, face, etc.
The problem is that I’m not sure what to do if the player owns all of a certain item. I want to give them the other items, but not that one. Should I just reduce the price of the lootbox or something? What if the player owns everything?
What do the people that use lootboxes here do when that stuff happens?
If they own everything, maybe just say “You own everything” Or even give them a badge for getting everything. 
Just my ideas.
Yeah, the problem is like I said my current system always gives you a certain amount of certain items.
For instance, you will always get 2 hats and 1 face in every lootbox. What should I do if they own all the hats, but not all the faces?
Even handling that in my code is turning out to be really messy. 
You can compensate them for the duplicate with some in-game currency.
That sounds way better than what I’m thinking of doing. I will highly consider this.
Yeah! Like Jailbreak lol
And like most games.
Okay since everyone does that I think I’ll do that. It also shouldn’t be too hard to add to my existing code. 
i don’t play most games. 
been real busy lately lol
Besides direct compensation for duplicates, you can implement fusion or merging of items for higher rarity. So, for example if you have the following:
Tier 1: 20 items
Tier 2: 15 items
Tier 3: 10 items
4 Tier 1 = 1 Tier 2
4 Tier 2 = 1 Tier 3
The implementation of a simple solution like this would make duplicates less of a problem and promote repurchasing of loot boxes with content that a user already has.