It would likely get voided as unconscionable if they just unilaterally demanded it, but it might hold up in specific circumstances (if the user is well-aware of

It would likely get voided as unconscionable if they just unilaterally demanded it, but it might hold up in specific circumstances (if the user is well-aware of the salary demand when they accepted the contract, and the user gets some proportionate value out of giving Apple a percentage of salary).