I'm a day or two behind on this (sorry), but for those commenting that you believe Magic Bands will eventually be phased out, I fully disagree. The guest benefit side of the technology can be easily replaced or replicated with countless "free" to Disney technologies, but that ignores the mountains of other useful features provided to Disney by the Magic Band. Perhaps the simplest of these being, Magic Bands remove a psychological barrier during purchasing. Tap your wrist doesn't equate to spending money in peoples mind, therefore the cash flows more readily.
Moving past the simple, Magic Bands allow Disney to harvest and mine massive amounts of raw data concerning nearly limitless different aspects of Guest's behavior while on site. They don't just know everywhere you go, everything you do, and everything you purchase, they know the order in which you do those things, they know which members of your party you are with. They know if you do Activity A and then activity B, and you stayed at Resort Q you are likely to do Y given the opportunity. They can then gently nudge you towards or away from that choice based on their own desire. Not only that, but they can nudge you in a manner that you are most likely to respond to, and, for that matter, enjoy. Magic Bands, and the data they provide, are worth far more than the few dollars they might cost to produce. They are the key that unlocks hundreds of more dollars in spending per family, they are the key that unlocks more personalized interactions, more individual experiences. They allow Disney to let loose the technology of AI video game engines to control the environment around you based on all of the past decisions you have ever made while on Disney property. Magic Bands aren't going anywhere, and although this may be bad for all of our wallets, it will be good for our enjoyment and experiences.
