The crafting rules. You spend at least 4 days to make an item for the same price you could have bought it for.
Oh, you can spend additional time to get the cost down to half, with the same rules as earn income? Well, you could also earn income the whole time, just buy the item and still have more money left than if you made it yourself.
I get that the rules are that way to prevent players from taking item balancing completely out of the GMs control with huge discounts. But it just feels bad for a player to invest into crafting only to be "allowed" to waste 4 extra days to essentially buy an item.