I suspect that part of what they do is look at your (likely very long) order history, and make the calculation that it's better to just reship rather than risk losing you as a customer. It's the benefit of having so much order activity over so much time - they know exactly how much a customer is worth to them. That's part of why this scam works - it trades on the existing goodwill / history of a longtime customer to get Amazon to do something un-economic.