The listing for Crafting Scrolls says, "You have to either Cast that Spell during the crafting process, or someone else must do so in your presence... The caster has to provide any cost of the spell."
And the listing for Crafting Wands says, "You have to either cast that spell during the process, or someone else must do so in your presence... The caster doesn’t need to pay any cost of the spell."
Okay... so if you're making a scroll you need to pay any associated costs with the spell being cast. And if you're making a wand, you cast the spell without needing to pay the cost of the associated spell. Seems odd, but at least that's clear to understand.
But what if the item you are crafting calls for a spell to be cast, but isn't a scroll or wand? Does the caster need to provide the cost of the spell or not?
Scrolls require you pay the cost because they don't cost anything when you do use them to cast the spell they contain, while wands require you to pay the spell's cost each time you cast it. It seems like the default would be that the spellcaster has to expend the cost of the spell when you craft the item, but based off of wands, I think that if the item still requires you to expend the cost of the spell then you shouldn't need to pay the cost when you craft the item.