May I suggest selling nickel versions of the blind box yoyos separately on their own. Nickel plated yoyos are a niche item, wanted by select individuals.
Certain people, such as myself, are allergic to nickel. I have owned nickel yoyos in the past and my palms get insanely itchy. I do not want to take the chance at getting a nickel version. That is one lottery that I wouldn't want to win, but would win.
They are sealed in a bag inside the box. Could always get one, cut the top of the bag and peak in first, if it's nickel then snap a photo of it in the bag and put it up for sale right away. You'll sell it really fast and make your money back, or trade it off for a color you want fairly quick