That's a subscription card. If someone buys the game, and signs up for a WoW subscription through their credit card, Gamestop gets no cut whatsoever.
Why should they? They're not hosting the WoW servers. They're not even processing the payments by that point.
I know this post is a bit old at this point, but here's the thing you are missing:
- I get Dropbox via the app store.
- I go to Dropbox.com to pay for more space.
- Apple does not get a cut.
*or*
- I get Dropbox via the app store.
- I use the app itself to pay for more space.
- Apple gets a cut.
This is no different than GameStop selling game time cards. If you pay with a CC on Blizzard's website, GameStop doesn't get a cut. But if you buy via GameStop, you do.
Apple is not saying "You must sell your stuff through us". But they are adamant that selling within the app on an Apple device is "selling through Apple". Netflix doesn't offer any in-app purchases, and they are let on. Why? Because they don't sell subscriptions through the app, the app is just a portal. That's the real crux of the issue here. Is Apple right to say that if you want to sell stuff through an app on their devices, that you are selling to the customer through Apple? Microsoft, interestingly enough, seems to follow the same stance with the XBox, although even more strict. You can't even post DLC or the like without Microsoft getting a cut. And then DLC cards in stores like GameStop gives them a cut on top of that.