Not that I'm suggesting you do this, but if you're going through the trouble of flying out to interview, you might as well do well. In the worst case, you are where you started, and in the best case you have a good offer that can give you leverage in other negotiations.
And when you take the other job instead, be sure to tell Amazon "It sounds like a great opportunity, but I have a comparable offer without your godawful sick policy." Amazon's doing this because they think the extra hours they'll squeeze out of employees outweighs the talent that it costs them.
Being doing this countless times, i always screw up onsites unintentionally though :(
Why would you screw up the interview? Just decline the offer.