I suggest a small change in wording on the custom apparel shop page, to make things more clear:
Change the purchase button to say preview instead, as the following pop-up is indeed a preview of the apparel. The preview pop-up can then have a purchase button (instead of confirm).
As things are now it’s not clear you can preview the items before purchasing, it took me a while to figure that out as I assumed clicking the purchase button would take my money right away. XD