Doesn't the last sentence the in parentheses say it is casting a spell?
The creator must have prepared the spell to be stored (or must know the spell, in the case of a sorcerer or bard) and must provide any focuses the spell requires. Fifty of each needed material component are required (one foreach charge). Material components are consumed when work begins, but focuses are not. A focus used in creating a wand can be reused. The act of working on the wand triggers the prepared spell, making it unavailable for casting during each day devoted to the wand’s creation. (That is, that spell slot is expended from the caster’s currently prepared spells, just as if it had been cast.)
Crafting a wand requires 1 day per each 1,000 gp of the price.