I agree that money probably isn't the thing. I would imagine the average Apple engineer would realize that the payment for leaking would have to be massive to offset the damage to career / loss of earnings from the damned good job they already have. Maybe it's the sense of getting away with something? Like a super lame, mundane version of Thomas Crown--life is going well in pretty much every category so raise a little hell just to see if you can?
One can be smart enough to work at Apple and also be dumb in a lot of ways. It's easy being manipulated ("nobody will know it was from you! you're a confidential source"), and it's definitely easy to think of yourself above all laws, or at least too smart to ever get caught.
