Wait? What?
Apple doesn't know what I buy. At least not currently. How can they know that? Only Mastercard and Visa know that.
Maybe Apple could buy that information from Mastercard or Visa? Is that what you're saying?
I'd wager that Google, Mastercard, Visa, and AT&T each know way more about me than Apple does. That's not even counting companies like Amazon, Target, etc. It seems to me that with respect to privacy, Apple is the least of my problems.
Apple has nearly nothing on you. Amex knows what I buy, when, and where.
Maybe they do know lots about me, maybe they don’t. A significant part of their public reputation rests on their respecting privacy concerns however. So if it turned out that they were secretly collecting data on me they would take a hit to their public reputation and (very likely) their bottom line.
They are very much incentivised to keep my data private and imho that offers a strong likelihood that they’ll actually do so.
Apple already has a lot more info on users then CCs do.
edit
Apple knows a lot about you IF you use apple products. Didn't think this would be a controversial point :)