In this case, you could first handle the creation of the blueprint (fluffed as research and development). So you're creating two magic items: first, the recipe for the item, then the item itself.
Creating a recipe or blueprint would likely be a lot harder than creating the item itself, especially since you can create copies of that item once you have the recipe. It's also why finding a recipe would be a lot easier than making one yourself.
So to create a recipe, you obviously wouldn't need a recipe for the recipe. But you'd probably still need a rare ingredient (consumed during R&D), crafting downtime, and a lot of gold. Something else might take the place of the recipe requirement, like a second rare ingredient, or more downtime or gold. Although, the recipe being one step rarer than the item it's for might also account for that.