The stolen CCs are not part of the laundering (that's just fraud/theft). I think it's easier to talk about laundering cash from drug sales. You buy an Apple Gift card with the cash. Use the gift card to buy jewels in an app you control, and now you have cleaned your drug money.

The challenge with doing this at scale on the App Store is the account requirement. Apple also likely has controls on how many gift cards you can redeem over a period of time. You also need an app that looks plausibly functional. The amount of money people supposedly spend on gems or whatever will help though.