I suspect this won't be the first game to offer in-app gold purchases and the like. That's worked well for some iOS games, and obviously they're trying to capitalize on that here, but there's a significant difference. The games on iOS where they do this are typically free or a buck, not $15 (or $10 minimum). Also the app store makes it clear when games have in-app purchases, and what the most popular ones are so they aren't a surprise. I haven't checked to see if the game is shown as having in-app purchases on Microsofts store.
That doesn't make them any less egregious on iOS. Actually, yes it does. If a game costs $1 and you love it, then giving the devs an extra buck doesn't seem so bad, you might even find that you want to give them an extra buck or two. I did that with Jetpack Joyride, an awesome game. I bought the "Counterfeit Machine" for 99 cents, still only making for a whopping $2 purchase.
Crimson is $10 at a minimum, more likely $15 (possibly more). Of course if gold purchases aren't really necessary to enjoy the game, then that's fine. If people want to do that, but nobody has to then it's fine with me.