Well, think about it - what do magic items cost? Gold and XP. And what do quests give you? Gold and XP.
So that's a possible solution right there. Instead of spending gold and XP on making items, you have to go on an appropriately difficult quest for rare components. The quest should be of a difficulty such that you would normally get the amount of Gold/XP from it that you need to make the item. But you don't get anything from the quest - you get to make the item instead.
This will tend to vary a lot. For scrolls, the quest might be quite small, possibly something like hunting in the woods for a rare kind of plant to make ink from, and possibly getting attacked by a bear or whatnot. For something like a Holy Avenger, you might need a feather from a Solar - which means either fighting one, or more likely (if you're the type to use a Holy Avenger) doing a quest for one.
Now sometimes players may be able to pull a fast one and get the components they need a lot more easily than you expected. That's not a big problem - just make the components for the next item they want that much tougher to get to compensate.