I'm sure Apple is not so stupid and sexist as to have business logic that gives men 10x the credit limit as women, other things being equal. My guess is that the credit limit depends on the person's reported individual income, so that if the husband earns more than the wife, which is still true in the majority of U.S. households, he gets a higher credit limit. If that is the explanation, I think it's a plausible, non-sexist way of setting a credit limit, although setting a credit limit based on household income is equally plausible.